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# Crypto#

    Stability: 2 - Stable

The `crypto` module provides cryptographic functionality that includes a set of wrappers for OpenSSL's hash, HMAC, cipher, decipher, sign and verify functions.

Use `require('crypto')` to access this module.

    const crypto = require('crypto');

    const secret = 'abcdefg';
    const hash = crypto.createHmac('sha256', secret)
                       .update('I love cupcakes')
                       .digest('hex');
    console.log(hash);
    // Prints:
    //   c0fa1bc00531bd78ef38c628449c5102aeabd49b5dc3a2a516ea6ea959d6658e

## Determining if crypto support is unavailable#

It is possible for Node.js to be built without including support for the `crypto` module. In such cases, calling `require('crypto')` will result in an error being thrown.

    var crypto;
    try {
      crypto = require('crypto');
    } catch (err) {
      console.log('crypto support is disabled!');
    }

## Class: Certificate#

Added in: v0.11.8

SPKAC is a Certificate Signing Request mechanism originally implemented by Netscape and now specified formally as part of HTML5's `keygen` element.

The `crypto` module provides the `Certificate` class for working with SPKAC data. The most common usage is handling output generated by the HTML5 `<keygen>` element. Node.js uses OpenSSL's SPKAC implementation internally.

### new crypto.Certificate()#

Instances of the `Certificate` class can be created using the `new` keyword or by calling `crypto.Certificate()` as a function:

    const crypto = require('crypto');

    const cert1 = new crypto.Certificate();
    const cert2 = crypto.Certificate();

### certificate.exportChallenge(spkac)#

Added in: v0.11.8

The `spkac` data structure includes a public key and a challenge. The `certificate.exportChallenge()` returns the challenge component in the form of a Node.js `Buffer`. The `spkac` argument can be either a string or a `Buffer`.

    const cert = require('crypto').Certificate();
    const spkac = getSpkacSomehow();
    const challenge = cert.exportChallenge(spkac);
    console.log(challenge.toString('utf8'));
    // Prints: the challenge as a UTF8 string

### certificate.exportPublicKey(spkac)#

Added in: v0.11.8

The `spkac` data structure includes a public key and a challenge. The `certificate.exportPublicKey()` returns the public key component in the form of a Node.js `Buffer`. The `spkac` argument can be either a string or a `Buffer`.

    const cert = require('crypto').Certificate();
    const spkac = getSpkacSomehow();
    const publicKey = cert.exportPublicKey(spkac);
    console.log(publicKey);
    // Prints: the public key as <Buffer ...>

### certificate.verifySpkac(spkac)#

Added in: v0.11.8

Returns `true` if the given `spkac` data structure is valid, `false` otherwise. The `spkac` argument must be a Node.js `Buffer`.

    const cert = require('crypto').Certificate();
    const spkac = getSpkacSomehow();
    console.log(cert.verifySpkac(Buffer.from(spkac)));
    // Prints: true or false

## Class: Cipher#

Added in: v0.1.94

Instances of the `Cipher` class are used to encrypt data. The class can be used in one of two ways:

- As a stream that is both readable and writable, where plain unencrypted data is written to produce encrypted data on the readable side, or
- Using the `cipher.update()` and `cipher.final()` methods to produce the encrypted data.

The `crypto.createCipher()` or `crypto.createCipheriv()` methods are used to create `Cipher` instances. `Cipher` objects are not to be created directly using the `new` keyword.

Example: Using `Cipher` objects as streams:

    const crypto = require('crypto');
    const cipher = crypto.createCipher('aes192', 'a password');

    var encrypted = '';
    cipher.on('readable', () => {
      var data = cipher.read();
      if (data)
        encrypted += data.toString('hex');
    });
    cipher.on('end', () => {
      console.log(encrypted);
      // Prints: ca981be48e90867604588e75d04feabb63cc007a8f8ad89b10616ed84d815504
    });

    cipher.write('some clear text data');
    cipher.end();

Example: Using `Cipher` and piped streams:

    const crypto = require('crypto');
    const fs = require('fs');
    const cipher = crypto.createCipher('aes192', 'a password');

    const input = fs.createReadStream('test.js');
    const output = fs.createWriteStream('test.enc');

    input.pipe(cipher).pipe(output);

Example: Using the `cipher.update()` and `cipher.final()` methods:

    const crypto = require('crypto');
    const cipher = crypto.createCipher('aes192', 'a password');

    var encrypted = cipher.update('some clear text data', 'utf8', 'hex');
    encrypted += cipher.final('hex');
    console.log(encrypted);
    // Prints: ca981be48e90867604588e75d04feabb63cc007a8f8ad89b10616ed84d815504

### cipher.final([output_encoding])#

Added in: v0.1.94

Returns any remaining enciphered contents. If `output_encoding` parameter is one of `'latin1'`, `'base64'` or `'hex'`, a string is returned. If an `output_encoding` is not provided, a `Buffer` is returned.

Once the `cipher.final()` method has been called, the `Cipher` object can no longer be used to encrypt data. Attempts to call `cipher.final()` more than once will result in an error being thrown.

### cipher.setAAD(buffer)#

Added in: v1.0.0

When using an authenticated encryption mode (only `GCM` is currently supported), the `cipher.setAAD()` method sets the value used for the additional authenticated data (AAD) input parameter.

Returns `this` for method chaining.

### cipher.getAuthTag()#

Added in: v1.0.0

When using an authenticated encryption mode (only `GCM` is currently supported), the `cipher.getAuthTag()` method returns a `Buffer` containing the authentication tag that has been computed from the given data.

The `cipher.getAuthTag()` method should only be called after encryption has been completed using the `cipher.final()` method.

### cipher.setAutoPadding(auto_padding=true)#

Added in: v0.7.1

When using block encryption algorithms, the `Cipher` class will automatically add padding to the input data to the appropriate block size. To disable the default padding call `cipher.setAutoPadding(false)`.

When `auto_padding` is `false`, the length of the entire input data must be a multiple of the cipher's block size or `cipher.final()` will throw an Error. Disabling automatic padding is useful for non-standard padding, for instance using `0x0` instead of PKCS padding.

The `cipher.setAutoPadding()` method must be called before `cipher.final()`.

Returns `this` for method chaining.

### cipher.update(data[, input_encoding][, output_encoding])#

Added in: v0.1.94

Updates the cipher with `data`. If the `input_encoding` argument is given, its value must be one of `'utf8'`, `'ascii'`, or `'latin1'` and the `data` argument is a string using the specified encoding. If the `input_encoding` argument is not given, `data` must be a `Buffer`. If `data` is a `Buffer` then `input_encoding` is ignored.

The `output_encoding` specifies the output format of the enciphered data, and can be `'latin1'`, `'base64'` or `'hex'`. If the `output_encoding` is specified, a string using the specified encoding is returned. If no `output_encoding` is provided, a `Buffer` is returned.

The `cipher.update()` method can be called multiple times with new data until `cipher.final()` is called. Calling `cipher.update()` after `cipher.final()` will result in an error being thrown.

## Class: Decipher#

Added in: v0.1.94

Instances of the `Decipher` class are used to decrypt data. The class can be used in one of two ways:

- As a stream that is both readable and writable, where plain encrypted data is written to produce unencrypted data on the readable side, or
- Using the `decipher.update()` and `decipher.final()` methods to produce the unencrypted data.

The `crypto.createDecipher()` or `crypto.createDecipheriv()` methods are used to create `Decipher` instances. `Decipher` objects are not to be created directly using the `new` keyword.

Example: Using `Decipher` objects as streams:

    const crypto = require('crypto');
    const decipher = crypto.createDecipher('aes192', 'a password');

    var decrypted = '';
    decipher.on('readable', () => {
      var data = decipher.read();
      if (data)
        decrypted += data.toString('utf8');
    });
    decipher.on('end', () => {
      console.log(decrypted);
      // Prints: some clear text data
    });

    var encrypted = 'ca981be48e90867604588e75d04feabb63cc007a8f8ad89b10616ed84d815504';
    decipher.write(encrypted, 'hex');
    decipher.end();

Example: Using `Decipher` and piped streams:

    const crypto = require('crypto');
    const fs = require('fs');
    const decipher = crypto.createDecipher('aes192', 'a password');

    const input = fs.createReadStream('test.enc');
    const output = fs.createWriteStream('test.js');

    input.pipe(decipher).pipe(output);

Example: Using the `decipher.update()` and `decipher.final()` methods:

    const crypto = require('crypto');
    const decipher = crypto.createDecipher('aes192', 'a password');

    var encrypted = 'ca981be48e90867604588e75d04feabb63cc007a8f8ad89b10616ed84d815504';
    var decrypted = decipher.update(encrypted, 'hex', 'utf8');
    decrypted += decipher.final('utf8');
    console.log(decrypted);
    // Prints: some clear text data

### decipher.final([output_encoding])#

Added in: v0.1.94

Returns any remaining deciphered contents. If `output_encoding` parameter is one of `'latin1'`, `'ascii'` or `'utf8'`, a string is returned. If an `output_encoding` is not provided, a `Buffer` is returned.

Once the `decipher.final()` method has been called, the `Decipher` object can no longer be used to decrypt data. Attempts to call `decipher.final()` more than once will result in an error being thrown.

### decipher.setAAD(buffer)#

Added in: v1.0.0

When using an authenticated encryption mode (only `GCM` is currently supported), the `decipher.setAAD()` method sets the value used for the additional authenticated data (AAD) input parameter.

Returns `this` for method chaining.

### decipher.setAuthTag(buffer)#

Added in: v1.0.0

When using an authenticated encryption mode (only `GCM` is currently supported), the `decipher.setAuthTag()` method is used to pass in the received authentication tag. If no tag is provided, or if the cipher text has been tampered with, `decipher.final()` with throw, indicating that the cipher text should be discarded due to failed authentication.

Returns `this` for method chaining.

### decipher.setAutoPadding(auto_padding=true)#

Added in: v0.7.1

When data has been encrypted without standard block padding, calling `decipher.setAutoPadding(false)` will disable automatic padding to prevent `decipher.final()` from checking for and removing padding.

Turning auto padding off will only work if the input data's length is a multiple of the ciphers block size.

The `decipher.setAutoPadding()` method must be called before `decipher.update()`.

Returns `this` for method chaining.

### decipher.update(data[, input_encoding][, output_encoding])#

Added in: v0.1.94

Updates the decipher with `data`. If the `input_encoding` argument is given, its value must be one of `'latin1'`, `'base64'`, or `'hex'` and the `data` argument is a string using the specified encoding. If the `input_encoding` argument is not given, `data` must be a `Buffer`. If `data` is a `Buffer` then `input_encoding` is ignored.

The `output_encoding` specifies the output format of the enciphered data, and can be `'latin1'`, `'ascii'` or `'utf8'`. If the `output_encoding` is specified, a string using the specified encoding is returned. If no `output_encoding` is provided, a `Buffer` is returned.

The `decipher.update()` method can be called multiple times with new data until `decipher.final()` is called. Calling `decipher.update()` after `decipher.final()` will result in an error being thrown.

## Class: DiffieHellman#

Added in: v0.5.0

The `DiffieHellman` class is a utility for creating Diffie-Hellman key exchanges.

Instances of the `DiffieHellman` class can be created using the `crypto.createDiffieHellman()` function.

    const crypto = require('crypto');
    const assert = require('assert');

    // Generate Alice's keys...
    const alice = crypto.createDiffieHellman(2048);
    const alice_key = alice.generateKeys();

    // Generate Bob's keys...
    const bob = crypto.createDiffieHellman(alice.getPrime(), alice.getGenerator());
    const bob_key = bob.generateKeys();

    // Exchange and generate the secret...
    const alice_secret = alice.computeSecret(bob_key);
    const bob_secret = bob.computeSecret(alice_key);

    // OK
    assert.equal(alice_secret.toString('hex'), bob_secret.toString('hex'));

### diffieHellman.computeSecret(other_public_key[, input_encoding][, output_encoding])#

Added in: v0.5.0

Computes the shared secret using `other_public_key` as the other party's public key and returns the computed shared secret. The supplied key is interpreted using the specified `input_encoding`, and secret is encoded using specified `output_encoding`. Encodings can be `'latin1'`, `'hex'`, or `'base64'`. If the `input_encoding` is not provided, `other_public_key` is expected to be a `Buffer`.

If `output_encoding` is given a string is returned; otherwise, a `Buffer` is returned.

### diffieHellman.generateKeys([encoding])#

Added in: v0.5.0

Generates private and public Diffie-Hellman key values, and returns the public key in the specified `encoding`. This key should be transferred to the other party. Encoding can be `'latin1'`, `'hex'`, or `'base64'`. If `encoding` is provided a string is returned; otherwise a `Buffer` is returned.

### diffieHellman.getGenerator([encoding])#

Added in: v0.5.0

Returns the Diffie-Hellman generator in the specified `encoding`, which can be `'latin1'`, `'hex'`, or `'base64'`. If `encoding` is provided a string is returned; otherwise a `Buffer` is returned.

### diffieHellman.getPrime([encoding])#

Added in: v0.5.0

Returns the Diffie-Hellman prime in the specified `encoding`, which can be `'latin1'`, `'hex'`, or `'base64'`. If `encoding` is provided a string is returned; otherwise a `Buffer` is returned.

### diffieHellman.getPrivateKey([encoding])#

Added in: v0.5.0

Returns the Diffie-Hellman private key in the specified `encoding`, which can be `'latin1'`, `'hex'`, or `'base64'`. If `encoding` is provided a string is returned; otherwise a `Buffer` is returned.

### diffieHellman.getPublicKey([encoding])#

Added in: v0.5.0

Returns the Diffie-Hellman public key in the specified `encoding`, which can be `'latin1'`, `'hex'`, or `'base64'`. If `encoding` is provided a string is returned; otherwise a `Buffer` is returned.

### diffieHellman.setPrivateKey(private_key[, encoding])#

Added in: v0.5.0

Sets the Diffie-Hellman private key. If the `encoding` argument is provided and is either `'latin1'`, `'hex'`, or `'base64'`, `private_key` is expected to be a string. If no `encoding` is provided, `private_key` is expected to be a `Buffer`.

### diffieHellman.setPublicKey(public_key[, encoding])#

Added in: v0.5.0

Sets the Diffie-Hellman public key. If the `encoding` argument is provided and is either `'latin1'`, `'hex'` or `'base64'`, `public_key` is expected to be a string. If no `encoding` is provided, `public_key` is expected to be a `Buffer`.

### diffieHellman.verifyError#

Added in: v0.11.12

A bit field containing any warnings and/or errors resulting from a check performed during initialization of the `DiffieHellman` object.

The following values are valid for this property (as defined in `constants` module):

- `DH_CHECK_P_NOT_SAFE_PRIME`
- `DH_CHECK_P_NOT_PRIME`
- `DH_UNABLE_TO_CHECK_GENERATOR`
- `DH_NOT_SUITABLE_GENERATOR`

## Class: ECDH#

Added in: v0.11.14

The `ECDH` class is a utility for creating Elliptic Curve Diffie-Hellman (ECDH) key exchanges.

Instances of the `ECDH` class can be created using the `crypto.createECDH()` function.

    const crypto = require('crypto');
    const assert = require('assert');

    // Generate Alice's keys...
    const alice = crypto.createECDH('secp521r1');
    const alice_key = alice.generateKeys();

    // Generate Bob's keys...
    const bob = crypto.createECDH('secp521r1');
    const bob_key = bob.generateKeys();

    // Exchange and generate the secret...
    const alice_secret = alice.computeSecret(bob_key);
    const bob_secret = bob.computeSecret(alice_key);

    assert(alice_secret, bob_secret);
      // OK

### ecdh.computeSecret(other_public_key[, input_encoding][, output_encoding])#

Added in: v0.11.14

Computes the shared secret using `other_public_key` as the other party's public key and returns the computed shared secret. The supplied key is interpreted using specified `input_encoding`, and the returned secret is encoded using the specified `output_encoding`. Encodings can be `'latin1'`, `'hex'`, or `'base64'`. If the `input_encoding` is not provided, `other_public_key` is expected to be a `Buffer`.

If `output_encoding` is given a string will be returned; otherwise a `Buffer` is returned.

### ecdh.generateKeys([encoding[, format]])#

Added in: v0.11.14

Generates private and public EC Diffie-Hellman key values, and returns the public key in the specified `format` and `encoding`. This key should be transferred to the other party.

The `format` argument specifies point encoding and can be `'compressed'` or `'uncompressed'`. If `format` is not specified, the point will be returned in `'uncompressed'` format.

The `encoding` argument can be `'latin1'`, `'hex'`, or `'base64'`. If `encoding` is provided a string is returned; otherwise a `Buffer` is returned.

### ecdh.getPrivateKey([encoding])#

Added in: v0.11.14

Returns the EC Diffie-Hellman private key in the specified `encoding`, which can be `'latin1'`, `'hex'`, or `'base64'`. If `encoding` is provided a string is returned; otherwise a `Buffer` is returned.

### ecdh.getPublicKey([encoding[, format]])#

Added in: v0.11.14

Returns the EC Diffie-Hellman public key in the specified `encoding` and `format`.

The `format` argument specifies point encoding and can be `'compressed'` or `'uncompressed'`. If `format` is not specified the point will be returned in `'uncompressed'` format.

The `encoding` argument can be `'latin1'`, `'hex'`, or `'base64'`. If `encoding` is specified, a string is returned; otherwise a `Buffer` is returned.

### ecdh.setPrivateKey(private_key[, encoding])#

Added in: v0.11.14

Sets the EC Diffie-Hellman private key. The `encoding` can be `'latin1'`, `'hex'` or `'base64'`. If `encoding` is provided, `private_key` is expected to be a string; otherwise `private_key` is expected to be a `Buffer`. If `private_key` is not valid for the curve specified when the `ECDH` object was created, an error is thrown. Upon setting the private key, the associated public point (key) is also generated and set in the ECDH object.

### ecdh.setPublicKey(public_key[, encoding])#

Added in: v0.11.14 Deprecated since: v5.2.0

    Stability: 0 - Deprecated

Sets the EC Diffie-Hellman public key. Key encoding can be `'latin1'`, `'hex'` or `'base64'`. If `encoding` is provided `public_key` is expected to be a string; otherwise a `Buffer` is expected.

Note that there is not normally a reason to call this method because `ECDH` only requires a private key and the other party's public key to compute the shared secret. Typically either `ecdh.generateKeys()` or `ecdh.setPrivateKey()` will be called. The `ecdh.setPrivateKey()` method attempts to generate the public point/key associated with the private key being set.

Example (obtaining a shared secret):

    const crypto = require('crypto');
    const alice = crypto.createECDH('secp256k1');
    const bob = crypto.createECDH('secp256k1');

    // Note: This is a shortcut way to specify one of Alice's previous private
    // keys. It would be unwise to use such a predictable private key in a real
    // application.
    alice.setPrivateKey(
      crypto.createHash('sha256').update('alice', 'utf8').digest()
    );

    // Bob uses a newly generated cryptographically strong
    // pseudorandom key pair bob.generateKeys();

    const alice_secret = alice.computeSecret(bob.getPublicKey(), null, 'hex');
    const bob_secret = bob.computeSecret(alice.getPublicKey(), null, 'hex');

    // alice_secret and bob_secret should be the same shared secret value
    console.log(alice_secret === bob_secret);

## Class: Hash#

Added in: v0.1.92

The `Hash` class is a utility for creating hash digests of data. It can be used in one of two ways:

- As a stream that is both readable and writable, where data is written to produce a computed hash digest on the readable side, or
- Using the `hash.update()` and `hash.digest()` methods to produce the computed hash.

The `crypto.createHash()` method is used to create `Hash` instances. `Hash` objects are not to be created directly using the `new` keyword.

Example: Using `Hash` objects as streams:

    const crypto = require('crypto');
    const hash = crypto.createHash('sha256');

    hash.on('readable', () => {
      var data = hash.read();
      if (data)
        console.log(data.toString('hex'));
        // Prints:
        //   6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50
    });

    hash.write('some data to hash');
    hash.end();

Example: Using `Hash` and piped streams:

    const crypto = require('crypto');
    const fs = require('fs');
    const hash = crypto.createHash('sha256');

    const input = fs.createReadStream('test.js');
    input.pipe(hash).pipe(process.stdout);

Example: Using the `hash.update()` and `hash.digest()` methods:

    const crypto = require('crypto');
    const hash = crypto.createHash('sha256');

    hash.update('some data to hash');
    console.log(hash.digest('hex'));
    // Prints:
    //   6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50

### hash.digest([encoding])#

Added in: v0.1.92

Calculates the digest of all of the data passed to be hashed (using the `hash.update()` method). The `encoding` can be `'hex'`, `'latin1'` or `'base64'`. If `encoding` is provided a string will be returned; otherwise a `Buffer` is returned.

The `Hash` object can not be used again after `hash.digest()` method has been called. Multiple calls will cause an error to be thrown.

### hash.update(data[, input_encoding])#

Added in: v0.1.92

Updates the hash content with the given `data`, the encoding of which is given in `input_encoding` and can be `'utf8'`, `'ascii'` or `'latin1'`. If `encoding` is not provided, and the `data` is a string, an encoding of `'utf8'` is enforced. If `data` is a `Buffer` then `input_encoding` is ignored.

This can be called many times with new data as it is streamed.

## Class: Hmac#

Added in: v0.1.94

The `Hmac` Class is a utility for creating cryptographic HMAC digests. It can be used in one of two ways:

- As a stream that is both readable and writable, where data is written to produce a computed HMAC digest on the readable side, or
- Using the `hmac.update()` and `hmac.digest()` methods to produce the computed HMAC digest.

The `crypto.createHmac()` method is used to create `Hmac` instances. `Hmac` objects are not to be created directly using the `new` keyword.

Example: Using `Hmac` objects as streams:

    const crypto = require('crypto');
    const hmac = crypto.createHmac('sha256', 'a secret');

    hmac.on('readable', () => {
      var data = hmac.read();
      if (data)
        console.log(data.toString('hex'));
        // Prints:
        //   7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e
    });

    hmac.write('some data to hash');
    hmac.end();

Example: Using `Hmac` and piped streams:

    const crypto = require('crypto');
    const fs = require('fs');
    const hmac = crypto.createHmac('sha256', 'a secret');

    const input = fs.createReadStream('test.js');
    input.pipe(hmac).pipe(process.stdout);

Example: Using the `hmac.update()` and `hmac.digest()` methods:

    const crypto = require('crypto');
    const hmac = crypto.createHmac('sha256', 'a secret');

    hmac.update('some data to hash');
    console.log(hmac.digest('hex'));
    // Prints:
    //   7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e

### hmac.digest([encoding])#

Added in: v0.1.94

Calculates the HMAC digest of all of the data passed using `hmac.update()`. The `encoding` can be `'hex'`, `'latin1'` or `'base64'`. If `encoding` is provided a string is returned; otherwise a `Buffer` is returned;

The `Hmac` object can not be used again after `hmac.digest()` has been called. Multiple calls to `hmac.digest()` will result in an error being thrown.

### hmac.update(data[, input_encoding])#

Added in: v0.1.94

Updates the `Hmac` content with the given `data`, the encoding of which is given in `input_encoding` and can be `'utf8'`, `'ascii'` or `'latin1'`. If `encoding` is not provided, and the `data` is a string, an encoding of `'utf8'` is enforced. If `data` is a `Buffer` then `input_encoding` is ignored.

This can be called many times with new data as it is streamed.

## Class: Sign#

Added in: v0.1.92

The `Sign` Class is a utility for generating signatures. It can be used in one of two ways:

- As a writable stream, where data to be signed is written and the `sign.sign()` method is used to generate and return the signature, or
- Using the `sign.update()` and `sign.sign()` methods to produce the signature.

The `crypto.createSign()` method is used to create `Sign` instances. `Sign` objects are not to be created directly using the `new` keyword.

Example: Using `Sign` objects as streams:

    const crypto = require('crypto');
    const sign = crypto.createSign('RSA-SHA256');

    sign.write('some data to sign');
    sign.end();

    const private_key = getPrivateKeySomehow();
    console.log(sign.sign(private_key, 'hex'));
    // Prints: the calculated signature

Example: Using the `sign.update()` and `sign.sign()` methods:

    const crypto = require('crypto');
    const sign = crypto.createSign('RSA-SHA256');

    sign.update('some data to sign');

    const private_key = getPrivateKeySomehow();
    console.log(sign.sign(private_key, 'hex'));
    // Prints: the calculated signature

A `Sign` instance can also be created by just passing in the digest algorithm name, in which case OpenSSL will infer the full signature algorithm from the type of the PEM-formatted private key, including algorithms that do not have directly exposed name constants, e.g. 'ecdsa-with-SHA256'.

Example: signing using ECDSA with SHA256

    const crypto = require('crypto');
    const sign = crypto.createSign('sha256');

    sign.update('some data to sign');

    const private_key = '-----BEGIN EC PRIVATE KEY-----\n' +
            'MHcCAQEEIF+jnWY1D5kbVYDNvxxo/Y+ku2uJPDwS0r/VuPZQrjjVoAoGCCqGSM49\n' +
            'AwEHoUQDQgAEurOxfSxmqIRYzJVagdZfMMSjRNNhB8i3mXyIMq704m2m52FdfKZ2\n' +
            'pQhByd5eyj3lgZ7m7jbchtdgyOF8Io/1ng==\n' +
            '-----END EC PRIVATE KEY-----\n';

    console.log(sign.sign(private_key).toString('hex'));

### sign.sign(private_key[, output_format])#

Added in: v0.1.92

Calculates the signature on all the data passed through using either `sign.update()` or `sign.write()`.

The `private_key` argument can be an object or a string. If `private_key` is a string, it is treated as a raw key with no passphrase. If `private_key` is an object, it is interpreted as a hash containing two properties:

- `key` : <String> - PEM encoded private key
- `passphrase` : <String> - passphrase for the private key

The `output_format` can specify one of `'latin1'`, `'hex'` or `'base64'`. If `output_format` is provided a string is returned; otherwise a `Buffer` is returned.

The `Sign` object can not be again used after `sign.sign()` method has been called. Multiple calls to `sign.sign()` will result in an error being thrown.

### sign.update(data[, input_encoding])#

Added in: v0.1.92

Updates the `Sign` content with the given `data`, the encoding of which is given in `input_encoding` and can be `'utf8'`, `'ascii'` or `'latin1'`. If `encoding` is not provided, and the `data` is a string, an encoding of `'utf8'` is enforced. If `data` is a `Buffer` then `input_encoding` is ignored.

This can be called many times with new data as it is streamed.

## Class: Verify#

Added in: v0.1.92

The `Verify` class is a utility for verifying signatures. It can be used in one of two ways:

- As a writable stream where written data is used to validate against the supplied signature, or
- Using the `verify.update()` and `verify.verify()` methods to verify the signature.

The [`crypto.createVerify()`][] method is used to create `Verify` instances. `Verify` objects are not to be created directly using the `new` keyword.

Example: Using `Verify` objects as streams:

    const crypto = require('crypto');
    const verify = crypto.createVerify('RSA-SHA256');

    verify.write('some data to sign');
    verify.end();

    const public_key = getPublicKeySomehow();
    const signature = getSignatureToVerify();
    console.log(verify.verify(public_key, signature));
    // Prints: true or false

Example: Using the `verify.update()` and `verify.verify()` methods:

    const crypto = require('crypto');
    const verify = crypto.createVerify('RSA-SHA256');

    verify.update('some data to sign');

    const public_key = getPublicKeySomehow();
    const signature = getSignatureToVerify();
    console.log(verify.verify(public_key, signature));
    // Prints: true or false

### verifier.update(data[, input_encoding])#

Added in: v0.1.92

Updates the `Verify` content with the given `data`, the encoding of which is given in `input_encoding` and can be `'utf8'`, `'ascii'` or `'latin1'`. If `encoding` is not provided, and the `data` is a string, an encoding of `'utf8'` is enforced. If `data` is a `Buffer` then `input_encoding` is ignored.

This can be called many times with new data as it is streamed.

### verifier.verify(object, signature[, signature_format])#

Added in: v0.1.92

Verifies the provided data using the given `object` and `signature`. The `object` argument is a string containing a PEM encoded object, which can be one an RSA public key, a DSA public key, or an X.509 certificate. The `signature` argument is the previously calculated signature for the data, in the `signature_format` which can be `'latin1'`, `'hex'` or `'base64'`. If a `signature_format` is specified, the `signature` is expected to be a string; otherwise `signature` is expected to be a `Buffer`.

Returns `true` or `false` depending on the validity of the signature for the data and public key.

The `verifier` object can not be used again after `verify.verify()` has been called. Multiple calls to `verify.verify()` will result in an error being thrown.

## `crypto` module methods and properties#

### crypto.constants#

Added in: v6.3.0

Returns an object containing commonly used constants for crypto and security related operations. The specific constants currently defined are described in Crypto Constants.

### crypto.DEFAULT_ENCODING#

Added in: v0.9.3

The default encoding to use for functions that can take either strings or buffers. The default value is `'buffer'`, which makes methods default to `Buffer` objects.

The `crypto.DEFAULT_ENCODING` mechanism is provided for backwards compatibility with legacy programs that expect `'latin1'` to be the default encoding.

New applications should expect the default to be `'buffer'`. This property may become deprecated in a future Node.js release.

### crypto.fips#

Added in: v6.0.0

Property for checking and controlling whether a FIPS compliant crypto provider is currently in use. Setting to true requires a FIPS build of Node.js.

### crypto.createCipher(algorithm, password)#

Added in: v0.1.94

Creates and returns a `Cipher` object that uses the given `algorithm` and `password`.

The `algorithm` is dependent on OpenSSL, examples are `'aes192'`, etc. On recent OpenSSL releases, `openssl list-cipher-algorithms` will display the available cipher algorithms.

The `password` is used to derive the cipher key and initialization vector (IV). The value must be either a `'latin1'` encoded string or a `Buffer`.

The implementation of `crypto.createCipher()` derives keys using the OpenSSL function `EVP_BytesToKey` with the digest algorithm set to MD5, one iteration, and no salt. The lack of salt allows dictionary attacks as the same password always creates the same key. The low iteration count and non-cryptographically secure hash algorithm allow passwords to be tested very rapidly.

In line with OpenSSL's recommendation to use pbkdf2 instead of `EVP_BytesToKey` it is recommended that developers derive a key and IV on their own using `crypto.pbkdf2()` and to use `crypto.createCipheriv()` to create the `Cipher` object.

### crypto.createCipheriv(algorithm, key, iv)#

Creates and returns a `Cipher` object, with the given `algorithm`, `key` and initialization vector (`iv`).

The `algorithm` is dependent on OpenSSL, examples are `'aes192'`, etc. On recent OpenSSL releases, `openssl list-cipher-algorithms` will display the available cipher algorithms.

The `key` is the raw key used by the `algorithm` and `iv` is an initialization vector. Both arguments must be `'utf8'` encoded strings or buffers.

### crypto.createCredentials(details)#

Added in: v0.1.92 Deprecated since: v0.11.13

    Stability: 0 - Deprecated: Use tls.createSecureContext() instead.

- `details` <Object> Identical to `tls.createSecureContext()`.

The `crypto.createCredentials()` method is a deprecated function for creating and returning a `tls.SecureContext`. It should not be used. Replace it with `tls.createSecureContext()` which has the exact same arguments and return value.

Returns a `tls.SecureContext`, as-if `tls.createSecureContext()` had been called.

### crypto.createDecipher(algorithm, password)#

Added in: v0.1.94

Creates and returns a `Decipher` object that uses the given `algorithm` and `password` (key).

The implementation of `crypto.createDecipher()` derives keys using the OpenSSL function `EVP_BytesToKey` with the digest algorithm set to MD5, one iteration, and no salt. The lack of salt allows dictionary attacks as the same password always creates the same key. The low iteration count and non-cryptographically secure hash algorithm allow passwords to be tested very rapidly.

In line with OpenSSL's recommendation to use pbkdf2 instead of `EVP_BytesToKey` it is recommended that developers derive a key and IV on their own using `crypto.pbkdf2()` and to use `crypto.createDecipheriv()` to create the `Decipher` object.

### crypto.createDecipheriv(algorithm, key, iv)#

Added in: v0.1.94

Creates and returns a `Decipher` object that uses the given `algorithm`, `key` and initialization vector (`iv`).

The `algorithm` is dependent on OpenSSL, examples are `'aes192'`, etc. On recent OpenSSL releases, `openssl list-cipher-algorithms` will display the available cipher algorithms.

The `key` is the raw key used by the `algorithm` and `iv` is an initialization vector. Both arguments must be `'utf8'` encoded strings or buffers.

### crypto.createDiffieHellman(prime[, prime_encoding][, generator][, generator_encoding])#

Added in: v0.11.12

Creates a `DiffieHellman` key exchange object using the supplied `prime` and an optional specific `generator`.

The `generator` argument can be a number, string, or `Buffer`. If `generator` is not specified, the value `2` is used.

The `prime_encoding` and `generator_encoding` arguments can be `'latin1'`, `'hex'`, or `'base64'`.

If `prime_encoding` is specified, `prime` is expected to be a string; otherwise a `Buffer` is expected.

If `generator_encoding` is specified, `generator` is expected to be a string; otherwise either a number or `Buffer` is expected.

### crypto.createDiffieHellman(prime_length[, generator])#

Added in: v0.5.0

Creates a `DiffieHellman` key exchange object and generates a prime of `prime_length` bits using an optional specific numeric `generator`. If `generator` is not specified, the value `2` is used.

### crypto.createECDH(curve_name)#

Added in: v0.11.14

Creates an Elliptic Curve Diffie-Hellman (`ECDH`) key exchange object using a predefined curve specified by the `curve_name` string. Use `crypto.getCurves()` to obtain a list of available curve names. On recent OpenSSL releases, `openssl ecparam -list_curves` will also display the name and description of each available elliptic curve.

### crypto.createHash(algorithm)#

Added in: v0.1.92

Creates and returns a `Hash` object that can be used to generate hash digests using the given `algorithm`.

The `algorithm` is dependent on the available algorithms supported by the version of OpenSSL on the platform. Examples are `'sha256'`, `'sha512'`, etc. On recent releases of OpenSSL, `openssl list-message-digest-algorithms` will display the available digest algorithms.

Example: generating the sha256 sum of a file

    const filename = process.argv[2];
    const crypto = require('crypto');
    const fs = require('fs');

    const hash = crypto.createHash('sha256');

    const input = fs.createReadStream(filename);
    input.on('readable', () => {
      var data = input.read();
      if (data)
        hash.update(data);
      else {
        console.log(`${hash.digest('hex')} ${filename}`);
      }
    });

### crypto.createHmac(algorithm, key)#

Added in: v0.1.94

Creates and returns an `Hmac` object that uses the given `algorithm` and `key`.

The `algorithm` is dependent on the available algorithms supported by the version of OpenSSL on the platform. Examples are `'sha256'`, `'sha512'`, etc. On recent releases of OpenSSL, `openssl list-message-digest-algorithms` will display the available digest algorithms.

The `key` is the HMAC key used to generate the cryptographic HMAC hash.

Example: generating the sha256 HMAC of a file

    const filename = process.argv[2];
    const crypto = require('crypto');
    const fs = require('fs');

    const hmac = crypto.createHmac('sha256', 'a secret');

    const input = fs.createReadStream(filename);
    input.on('readable', () => {
      var data = input.read();
      if (data)
        hmac.update(data);
      else {
        console.log(`${hmac.digest('hex')} ${filename}`);
      }
    });

### crypto.createSign(algorithm)#

Added in: v0.1.92

Creates and returns a `Sign` object that uses the given `algorithm`. Use `crypto.getHashes()` to obtain an array of names of the available signing algorithms.

### crypto.createVerify(algorithm)#

Added in: v0.1.92

Creates and returns a `Verify` object that uses the given algorithm. Use `crypto.getHashes()` to obtain an array of names of the available signing algorithms.

### crypto.getCiphers()#

Added in: v0.9.3

Returns an array with the names of the supported cipher algorithms.

Example:

    const ciphers = crypto.getCiphers();
    console.log(ciphers); // ['aes-128-cbc', 'aes-128-ccm', ...]

### crypto.getCurves()#

Added in: v2.3.0

Returns an array with the names of the supported elliptic curves.

Example:

    const curves = crypto.getCurves();
    console.log(curves); // ['secp256k1', 'secp384r1', ...]

### crypto.getDiffieHellman(group_name)#

Added in: v0.7.5

Creates a predefined `DiffieHellman` key exchange object. The supported groups are: `'modp1'`, `'modp2'`, `'modp5'` (defined in RFC 2412, but see Caveats) and `'modp14'`, `'modp15'`, `'modp16'`, `'modp17'`, `'modp18'` (defined in RFC 3526). The returned object mimics the interface of objects created by `crypto.createDiffieHellman()`, but will not allow changing the keys (with `diffieHellman.setPublicKey()` for example). The advantage of using this method is that the parties do not have to generate nor exchange a group modulus beforehand, saving both processor and communication time.

Example (obtaining a shared secret):

    const crypto = require('crypto');
    const alice = crypto.getDiffieHellman('modp14');
    const bob = crypto.getDiffieHellman('modp14');

    alice.generateKeys();
    bob.generateKeys();

    const alice_secret = alice.computeSecret(bob.getPublicKey(), null, 'hex');
    const bob_secret = bob.computeSecret(alice.getPublicKey(), null, 'hex');

    /* alice_secret and bob_secret should be the same */
    console.log(alice_secret == bob_secret);

### crypto.getHashes()#

Added in: v0.9.3

Returns an array of the names of the supported hash algorithms, such as `RSA-SHA256`.

Example:

    const hashes = crypto.getHashes();
    console.log(hashes); // ['sha', 'sha1', 'sha1WithRSAEncryption', ...]

### crypto.pbkdf2(password, salt, iterations, keylen, digest, callback)#

Added in: v0.5.5

Provides an asynchronous Password-Based Key Derivation Function 2 (PBKDF2) implementation. A selected HMAC digest algorithm specified by `digest` is applied to derive a key of the requested byte length (`keylen`) from the `password`, `salt` and `iterations`.

The supplied `callback` function is called with two arguments: `err` and `derivedKey`. If an error occurs, `err` will be set; otherwise `err` will be null. The successfully generated `derivedKey` will be passed as a `Buffer`.

The `iterations` argument must be a number set as high as possible. The higher the number of iterations, the more secure the derived key will be, but will take a longer amount of time to complete.

The `salt` should also be as unique as possible. It is recommended that the salts are random and their lengths are greater than 16 bytes. See NIST SP 800-132 for details.

Example:

    const crypto = require('crypto');
    crypto.pbkdf2('secret', 'salt', 100000, 512, 'sha512', (err, key) => {
      if (err) throw err;
      console.log(key.toString('hex'));  // 'c5e478d...1469e50'
    });

An array of supported digest functions can be retrieved using `crypto.getHashes()`.

### crypto.pbkdf2Sync(password, salt, iterations, keylen, digest)#

Added in: v0.9.3

Provides a synchronous Password-Based Key Derivation Function 2 (PBKDF2) implementation. A selected HMAC digest algorithm specified by `digest` is applied to derive a key of the requested byte length (`keylen`) from the `password`, `salt` and `iterations`.

If an error occurs an Error will be thrown, otherwise the derived key will be returned as a `Buffer`.

The `iterations` argument must be a number set as high as possible. The higher the number of iterations, the more secure the derived key will be, but will take a longer amount of time to complete.

The `salt` should also be as unique as possible. It is recommended that the salts are random and their lengths are greater than 16 bytes. See NIST SP 800-132 for details.

Example:

    const crypto = require('crypto');
    const key = crypto.pbkdf2Sync('secret', 'salt', 100000, 512, 'sha512');
    console.log(key.toString('hex'));  // 'c5e478d...1469e50'

An array of supported digest functions can be retrieved using `crypto.getHashes()`.

### crypto.privateDecrypt(private_key, buffer)#

Added in: v0.11.14

Decrypts `buffer` with `private_key`.

`private_key` can be an object or a string. If `private_key` is a string, it is treated as the key with no passphrase and will use `RSA_PKCS1_OAEP_PADDING`. If `private_key` is an object, it is interpreted as a hash object with the keys:

- `key` : <String> - PEM encoded private key
- `passphrase` : <String> - Optional passphrase for the private key
- `padding` : An optional padding value, one of the following:
  - `crypto.constants.RSA_NO_PADDING`
  - `crypto.constants.RSA_PKCS1_PADDING`
  - `crypto.constants.RSA_PKCS1_OAEP_PADDING`

All paddings are defined in `crypto.constants`.

### crypto.timingSafeEqual(a, b)#

Added in: v6.6.0

Returns true if `a` is equal to `b`, without leaking timing information that would allow an attacker to guess one of the values. This is suitable for comparing HMAC digests or secret values like authentication cookies or capability urls.

`a` and `b` must both be `Buffer`s, and they must have the same length.

Note: Use of `crypto.timingSafeEqual` does not guarantee that the surrounding code is timing-safe. Care should be taken to ensure that the surrounding code does not introduce timing vulnerabilities.

### crypto.privateEncrypt(private_key, buffer)#

Added in: v1.1.0

Encrypts `buffer` with `private_key`.

`private_key` can be an object or a string. If `private_key` is a string, it is treated as the key with no passphrase and will use `RSA_PKCS1_PADDING`. If `private_key` is an object, it is interpreted as a hash object with the keys:

- `key` : <String> - PEM encoded private key
- `passphrase` : <String> - Optional passphrase for the private key
- `padding` : An optional padding value, one of the following:
  - `crypto.constants.RSA_NO_PADDING`
  - `crypto.constants.RSA_PKCS1_PADDING`

All paddings are defined in `crypto.constants`.

### crypto.publicDecrypt(public_key, buffer)#

Added in: v1.1.0

Decrypts `buffer` with `public_key`.

`public_key` can be an object or a string. If `public_key` is a string, it is treated as the key with no passphrase and will use `RSA_PKCS1_PADDING`. If `public_key` is an object, it is interpreted as a hash object with the keys:

- `key` : <String> - PEM encoded public key
- `passphrase` : <String> - Optional passphrase for the private key
- `padding` : An optional padding value, one of the following:
  - `crypto.constants.RSA_NO_PADDING`
  - `crypto.constants.RSA_PKCS1_PADDING`
  - `crypto.constants.RSA_PKCS1_OAEP_PADDING`

Because RSA public keys can be derived from private keys, a private key may be passed instead of a public key.

All paddings are defined in `crypto.constants`.

### crypto.publicEncrypt(public_key, buffer)#

Added in: v0.11.14

Encrypts `buffer` with `public_key`.

`public_key` can be an object or a string. If `public_key` is a string, it is treated as the key with no passphrase and will use `RSA_PKCS1_OAEP_PADDING`. If `public_key` is an object, it is interpreted as a hash object with the keys:

- `key` : <String> - PEM encoded public key
- `passphrase` : <String> - Optional passphrase for the private key
- `padding` : An optional padding value, one of the following:
  - `crypto.constants.RSA_NO_PADDING`
  - `crypto.constants.RSA_PKCS1_PADDING`
  - `crypto.constants.RSA_PKCS1_OAEP_PADDING`

Because RSA public keys can be derived from private keys, a private key may be passed instead of a public key.

All paddings are defined in `crypto.constants`.

### crypto.randomBytes(size[, callback])#

Added in: v0.5.8

Generates cryptographically strong pseudo-random data. The `size` argument is a number indicating the number of bytes to generate.

If a `callback` function is provided, the bytes are generated asynchronously and the `callback` function is invoked with two arguments: `err` and `buf`. If an error occurs, `err` will be an Error object; otherwise it is null. The `buf` argument is a `Buffer` containing the generated bytes.

    // Asynchronous
    const crypto = require('crypto');
    crypto.randomBytes(256, (err, buf) => {
      if (err) throw err;
      console.log(`${buf.length} bytes of random data: ${buf.toString('hex')}`);
    });

If the `callback` function is not provided, the random bytes are generated synchronously and returned as a `Buffer`. An error will be thrown if there is a problem generating the bytes.

    // Synchronous
    const buf = crypto.randomBytes(256);
    console.log(
      `${buf.length} bytes of random data: ${buf.toString('hex')}`);

The `crypto.randomBytes()` method will block until there is sufficient entropy. This should normally never take longer than a few milliseconds. The only time when generating the random bytes may conceivably block for a longer period of time is right after boot, when the whole system is still low on entropy.

### crypto.setEngine(engine[, flags])#

Added in: v0.11.11

Load and set the `engine` for some or all OpenSSL functions (selected by flags).

`engine` could be either an id or a path to the engine's shared library.

The optional `flags` argument uses `ENGINE_METHOD_ALL` by default. The `flags` is a bit field taking one of or a mix of the following flags (defined in `crypto.constants`):

- `crypto.constants.ENGINE_METHOD_RSA`
- `crypto.constants.ENGINE_METHOD_DSA`
- `crypto.constants.ENGINE_METHOD_DH`
- `crypto.constants.ENGINE_METHOD_RAND`
- `crypto.constants.ENGINE_METHOD_ECDH`
- `crypto.constants.ENGINE_METHOD_ECDSA`
- `crypto.constants.ENGINE_METHOD_CIPHERS`
- `crypto.constants.ENGINE_METHOD_DIGESTS`
- `crypto.constants.ENGINE_METHOD_STORE`
- `crypto.constants.ENGINE_METHOD_PKEY_METHS`
- `crypto.constants.ENGINE_METHOD_PKEY_ASN1_METHS`
- `crypto.constants.ENGINE_METHOD_ALL`
- `crypto.constants.ENGINE_METHOD_NONE`

## Notes#

### Legacy Streams API (pre Node.js v0.10)#

The Crypto module was added to Node.js before there was the concept of a unified Stream API, and before there were `Buffer` objects for handling binary data. As such, the many of the `crypto` defined classes have methods not typically found on other Node.js classes that implement the streams API (e.g. `update()`, `final()`, or `digest()`). Also, many methods accepted and returned `'latin1'` encoded strings by default rather than Buffers. This default was changed after Node.js v0.8 to use `Buffer` objects by default instead.

### Recent ECDH Changes#

Usage of `ECDH` with non-dynamically generated key pairs has been simplified. Now, `ecdh.setPrivateKey()` can be called with a preselected private key and the associated public point (key) will be computed and stored in the object. This allows code to only store and provide the private part of the EC key pair. `ecdh.setPrivateKey()` now also validates that the private key is valid for the selected curve.

The `ecdh.setPublicKey()` method is now deprecated as its inclusion in the API is not useful. Either a previously stored private key should be set, which automatically generates the associated public key, or `ecdh.generateKeys()` should be called. The main drawback of using `ecdh.setPublicKey()` is that it can be used to put the ECDH key pair into an inconsistent state.

### Support for weak or compromised algorithms#

The `crypto` module still supports some algorithms which are already compromised and are not currently recommended for use. The API also allows the use of ciphers and hashes with a small key size that are considered to be too weak for safe use.

Users should take full responsibility for selecting the crypto algorithm and key size according to their security requirements.

Based on the recommendations of NIST SP 800-131A:

- MD5 and SHA-1 are no longer acceptable where collision resistance is required such as digital signatures.
- The key used with RSA, DSA and DH algorithms is recommended to have at least 2048 bits and that of the curve of ECDSA and ECDH at least 224 bits, to be safe to use for several years.
- The DH groups of `modp1`, `modp2` and `modp5` have a key size smaller than 2048 bits and are not recommended.

See the reference for other recommendations and details.

## Crypto Constants#

The following constants exported by `crypto.constants` apply to various uses of the `crypto`, `tls`, and `https` modules and are generally specific to OpenSSL.

### OpenSSL Options#

Constant | Description
--- | ---
`SSL_OP_ALL` | Applies multiple bug workarounds within OpenSSL. See https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html for detail.
`SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION` | Allows legacy insecure renegotiation between OpenSSL and unpatched clients or servers. See https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html.
`SSL_OP_CIPHER_SERVER_PREFERENCE` | Attempts to use the server's preferences instead of the client's when selecting a cipher. Behaviour depends on protocol version. See https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html.
`SSL_OP_CISCO_ANYCONNECT` | Instructs OpenSSL to use Cisco's "speshul" version of DTLS_BAD_VER.
`SSL_OP_COOKIE_EXCHANGE` | Instructs OpenSSL to turn on cookie exchange.
`SSL_OP_CRYPTOPRO_TLSEXT_BUG` | Instructs OpenSSL to add server-hello extension from an early version of the cryptopro draft.
`SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS` | Instructs OpenSSL to disable a SSL 3.0/TLS 1.0 vulnerability workaround added in OpenSSL 0.9.6d.
`SSL_OP_EPHEMERAL_RSA` | Instructs OpenSSL to always use the tmp_rsa key when performing RSA operations.
`SSL_OP_LEGACY_SERVER_CONNECT` | Allows initial connection to servers that do not support RI.
`SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER` |
`SSL_OP_MICROSOFT_SESS_ID_BUG` |
`SSL_OP_MSIE_SSLV2_RSA_PADDING` | Instructs OpenSSL to disable the workaround for a man-in-the-middle protocol-version vulnerability in the SSL 2.0 server implementation.
`SSL_OP_NETSCAPE_CA_DN_BUG` |
`SSL_OP_NETSCAPE_CHALLENGE_BUG` |
`SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG` |
`SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG` |
`SSL_OP_NO_COMPRESSION` | Instructs OpenSSL to disable support for SSL/TLS compression.
`SSL_OP_NO_QUERY_MTU` |
`SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION` | Instructs OpenSSL to always start a new session when performing renegotiation.
`SSL_OP_NO_SSLv2` | Instructs OpenSSL to turn off SSL v2
`SSL_OP_NO_SSLv3` | Instructs OpenSSL to turn off SSL v3
`SSL_OP_NO_TICKET` | Instructs OpenSSL to disable use of RFC4507bis tickets.
`SSL_OP_NO_TLSv1` | Instructs OpenSSL to turn off TLS v1
`SSL_OP_NO_TLSv1_1` | Instructs OpenSSL to turn off TLS v1.1
`SSL_OP_NO_TLSv1_2` | Instructs OpenSSL to turn off TLS v1.2
| `SSL_OP_PKCS1_CHECK_1` |
`SSL_OP_PKCS1_CHECK_2` |
`SSL_OP_SINGLE_DH_USE` | Instructs OpenSSL to always create a new key when using temporary/ephemeral DH parameters.
`SSL_OP_SINGLE_ECDH_USE` | Instructs OpenSSL to always create a new key when using temporary/ephemeral ECDH parameters.
| `SSL_OP_SSLEAY_080_CLIENT_DH_BUG` |
`SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG` |
`SSL_OP_TLS_BLOCK_PADDING_BUG` |
`SSL_OP_TLS_D5_BUG` |
`SSL_OP_TLS_ROLLBACK_BUG` | Instructs OpenSSL to disable version rollback attack detection.

### OpenSSL Engine Constants#

Constant | Description
--- | ---
`ENGINE_METHOD_RSA` | Limit engine usage to RSA
`ENGINE_METHOD_DSA` | Limit engine usage to DSA
`ENGINE_METHOD_DH` | Limit engine usage to DH
`ENGINE_METHOD_RAND` | Limit engine usage to RAND
`ENGINE_METHOD_ECDH` | Limit engine usage to ECDH
`ENGINE_METHOD_ECDSA` | Limit engine usage to ECDSA
`ENGINE_METHOD_CIPHERS` | Limit engine usage to CIPHERS
`ENGINE_METHOD_DIGESTS` | Limit engine usage to DIGESTS
`ENGINE_METHOD_STORE` | Limit engine usage to STORE
`ENGINE_METHOD_PKEY_METHS` | Limit engine usage to PKEY_METHDS
`ENGINE_METHOD_PKEY_ASN1_METHS` | Limit engine usage to PKEY_ASN1_METHS
`ENGINE_METHOD_ALL` |
`ENGINE_METHOD_NONE` |

### Other OpenSSL Constants#

Constant | Description
--- | ---
`DH_CHECK_P_NOT_SAFE_PRIME` |
`DH_CHECK_P_NOT_PRIME` |
`DH_UNABLE_TO_CHECK_GENERATOR` |
`DH_NOT_SUITABLE_GENERATOR` |
`NPN_ENABLED` |
`ALPN_ENABLED` |
`RSA_PKCS1_PADDING` |
`RSA_SSLV23_PADDING` |
`RSA_NO_PADDING` |
`RSA_PKCS1_OAEP_PADDING` |
`RSA_X931_PADDING` |
`RSA_PKCS1_PSS_PADDING` |
`POINT_CONVERSION_COMPRESSED` |
`POINT_CONVERSION_UNCOMPRESSED` |
`POINT_CONVERSION_HYBRID` |

### Node.js Crypto Constants#

Constant | Description
--- | ---
`defaultCoreCipherList` | Specifies the built-in default cipher list used by Node.js.
`defaultCipherList` | Specifies the active default cipher list used by the current Node.js process.