Node.js v5.12.0 Documentation

Table of Contents

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

Class: Certificate#

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)#

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)#

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)#

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(new Buffer(spkac)));
  // Prints true or false

Class: Cipher#

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])#

Returns any remaining enciphered contents. If output_encoding parameter is one of 'binary', '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)#

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.

cipher.getAuthTag()#

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)#

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().

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

Updates the cipher with data. If the input_encoding argument is given, it's value must be one of 'utf8', 'ascii', or 'binary' 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 'binary', '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#

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])#

Returns any remaining deciphered contents. If output_encoding parameter is one of 'binary', 'base64' or 'hex', 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)#

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.

decipher.setAuthTag(buffer)#

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.

decipher.setAutoPadding(auto_padding=true)#

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().

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

Updates the decipher with data. If the input_encoding argument is given, it's value must be one of 'binary', '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 'binary', '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#

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])#

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 'binary', '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])#

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 'binary', 'hex', or 'base64'. If encoding is provided a string is returned; otherwise a Buffer is returned.

diffieHellman.getGenerator([encoding])#

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

diffieHellman.getPrime([encoding])#

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

diffieHellman.getPrivateKey([encoding])#

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

diffieHellman.getPublicKey([encoding])#

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

diffieHellman.setPrivateKey(private_key[, encoding])#

Sets the Diffie-Hellman private key. If the encoding argument is provided and is either 'binary', '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])#

Sets the Diffie-Hellman public key. If the encoding argument is provided and is either 'binary', '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#

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#

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])#

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 'binary', '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]])#

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

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

ecdh.getPrivateKey([encoding])#

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

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

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

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

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

ecdh.setPrivateKey(private_key[, encoding])#

Sets the EC Diffie-Hellman private key. The encoding can be 'binary', '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])#

Stability: 0 - Deprecated

Sets the EC Diffie-Hellman public key. Key encoding can be 'binary', '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#

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])#

Calculates the digest of all of the data passed to be hashed (using the hash.update() method). The encoding can be 'hex', 'binary' 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])#

Updates the hash content with the given data, the encoding of which is given in input_encoding and can be 'utf8', 'ascii' or 'binary'. If encoding is not provided, and the data is a string, an encoding of 'binary' 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#

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])#

Calculates the HMAC digest of all of the data passed using hmac.update(). The encoding can be 'hex', 'binary' 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])#

Updates the Hmac content with the given data, the encoding of which is given in input_encoding and can be 'utf8', 'ascii' or 'binary'. 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#

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])#

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 'binary', 'hex' or 'base64'. If output_format is provided a string is returned; otherwise a Buffer is returned.