nodejs/doc/api/crypto.markdown

Crypto

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

The crypto module requires OpenSSL to be available on the underlying platform. It offers a way of encapsulating secure credentials to be used as part of a secure HTTPS net or http connection.

It also offers a set of wrappers for OpenSSL's hash, hmac, cipher, decipher, sign and verify methods.

crypto.createCredentials(details)

Creates a credentials object, with the optional details being a dictionary with keys:

• key : a string holding the PEM encoded private key
• cert : a string holding the PEM encoded certificate
• ca : either a string or list of strings of PEM encoded CA certificates to trust.

If no 'ca' details are given, then node.js will use the default publicly trusted list of CAs as given in http://mxr.mozilla.org/mozilla/source/security/nss/lib/ckfw/builtins/certdata.txt.

crypto.createHash(algorithm)

Creates and returns a hash object, a cryptographic hash with the given algorithm which can be used to generate hash digests.

algorithm is dependent on the available algorithms supported by the version of OpenSSL on the platform. Examples are 'sha1', 'md5', 'sha256', 'sha512', etc. On recent releases, openssl list-message-digest-algorithms will display the available digest algorithms.

Example: this program that takes the sha1 sum of a file

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

var shasum = crypto.createHash('sha1');

var s = fs.ReadStream(filename);
s.on('data', function(d) {
  shasum.update(d);
});

s.on('end', function() {
  var d = shasum.digest('hex');
  console.log(d + '  ' + filename);
});

hash.update(data)

Updates the hash content with the given data. This can be called many times with new data as it is streamed.

hash.digest(encoding='binary')

Calculates the digest of all of the passed data to be hashed. The encoding can be 'hex', 'binary' or 'base64'.

Note: hash object can not be used after digest() method been called.

crypto.createHmac(algorithm, key)

Creates and returns a hmac object, a cryptographic hmac with the given algorithm and key.

algorithm is dependent on the available algorithms supported by OpenSSL - see createHash above. key is the hmac key to be used.

hmac.update(data)

Update the hmac content with the given data. This can be called many times with new data as it is streamed.

hmac.digest(encoding='binary')

Calculates the digest of all of the passed data to the hmac. The encoding can be 'hex', 'binary' or 'base64'.

Note: hmac object can not be used after digest() method been called.

crypto.createCipher(algorithm, password)

Creates and returns a cipher object, with the given algorithm and password.

algorithm is dependent on OpenSSL, examples are 'aes192', etc. On recent releases, openssl list-cipher-algorithms will display the available cipher algorithms. password is used to derive key and IV, which must be 'binary' encoded string (See the Buffers for more information).

crypto.createCipheriv(algorithm, key, iv)

Creates and returns a cipher object, with the given algorithm, key and iv.

algorithm is the same as the createCipher(). key is a raw key used in algorithm. iv is an Initialization vector. key and iv must be 'binary' encoded string (See the Buffers for more information).

cipher.update(data, input_encoding='binary', output_encoding='binary')

Updates the cipher with data, the encoding of which is given in input_encoding and can be 'utf8', 'ascii' or 'binary'. The output_encoding specifies the output format of the enciphered data, and can be 'binary', 'base64' or 'hex'.

Returns the enciphered contents, and can be called many times with new data as it is streamed.

cipher.final(output_encoding='binary')

Returns any remaining enciphered contents, with output_encoding being one of: 'binary', 'base64' or 'hex'.

Note: cipher object can not be used after final() method been called.

crypto.createDecipher(algorithm, password)

Creates and returns a decipher object, with the given algorithm and key. This is the mirror of the createCipher() above.

crypto.createDecipheriv(algorithm, key, iv)

Creates and returns a decipher object, with the given algorithm, key and iv. This is the mirror of the createCipheriv() above.

decipher.update(data, input_encoding='binary', output_encoding='binary')

Updates the decipher with data, which is encoded in 'binary', 'base64' or 'hex'. The output_decoding specifies in what format to return the deciphered plaintext: 'binary', 'ascii' or 'utf8'.

decipher.final(output_encoding='binary')

Returns any remaining plaintext which is deciphered, with output_encoding being one of: 'binary', 'ascii' or 'utf8'.

Note: decipher object can not be used after final() method been called.

crypto.createSign(algorithm)

Creates and returns a signing object, with the given algorithm. On recent OpenSSL releases, openssl list-public-key-algorithms will display the available signing algorithms. Examples are 'RSA-SHA256'.

signer.update(data)

Updates the signer object with data. This can be called many times with new data as it is streamed.

signer.sign(private_key, output_format='binary')

Calculates the signature on all the updated data passed through the signer. private_key is a string containing the PEM encoded private key for signing.

Returns the signature in output_format which can be 'binary', 'hex' or 'base64'.

Note: signer object can not be used after sign() method been called.

crypto.createVerify(algorithm)

Creates and returns a verification object, with the given algorithm. This is the mirror of the signing object above.

verifier.update(data)

Updates the verifier object with data. This can be called many times with new data as it is streamed.

verifier.verify(object, signature, signature_format='binary')

Verifies the signed data by using the object and signature. object is a string containing a PEM encoded object, which can be one of RSA public key, DSA public key, or X.509 certificate. signature is the previously calculated signature for the data, in the signature_format which can be 'binary', 'hex' or 'base64'.

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

Note: verifier object can not be used after verify() method been called.

crypto.createDiffieHellman(prime_length)

Creates a Diffie-Hellman key exchange object and generates a prime of the given bit length. The generator used is 2.

crypto.createDiffieHellman(prime, encoding='binary')

Creates a Diffie-Hellman key exchange object using the supplied prime. The generator used is 2. Encoding can be 'binary', 'hex', or 'base64'.

diffieHellman.generateKeys(encoding='binary')

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'.

diffieHellman.computeSecret(other_public_key, input_encoding='binary', output_encoding=input_encoding)

Computes the shared secret using other_public_key as the other party's public key and returns the computed shared secret. Supplied key is interpreted using specified input_encoding, and secret is encoded using specified output_encoding. Encodings can be 'binary', 'hex', or 'base64'. If no output encoding is given, the input encoding is used as output encoding.

diffieHellman.getPrime(encoding='binary')

Returns the Diffie-Hellman prime in the specified encoding, which can be 'binary', 'hex', or 'base64'.

diffieHellman.getGenerator(encoding='binary')

Returns the Diffie-Hellman prime in the specified encoding, which can be 'binary', 'hex', or 'base64'.

diffieHellman.getPublicKey(encoding='binary')

Returns the Diffie-Hellman public key in the specified encoding, which can be 'binary', 'hex', or 'base64'.

diffieHellman.getPrivateKey(encoding='binary')

Returns the Diffie-Hellman private key in the specified encoding, which can be 'binary', 'hex', or 'base64'.

diffieHellman.setPublicKey(public_key, encoding='binary')

Sets the Diffie-Hellman public key. Key encoding can be 'binary', 'hex', or 'base64'.

diffieHellman.setPrivateKey(public_key, encoding='binary')

Sets the Diffie-Hellman private key. Key encoding can be 'binary', 'hex', or 'base64'.

pbkdf2(password, salt, iterations, keylen, callback)

Asynchronous PBKDF2 applies pseudorandom function HMAC-SHA1 to derive a key of given length from the given password, salt and iterations. The callback gets two arguments (err, derivedKey).

randomBytes(size, [callback])

Generates cryptographically strong pseudo-random data. Usage:

// async
crypto.randomBytes(256, function(ex, buf) {
  if (ex) throw ex;
  console.log('Have %d bytes of random data: %s', buf.length, buf);
});

// sync
try {
  var buf = crypto.randomBytes(256);
  console.log('Have %d bytes of random data: %s', buf.length, buf);
} catch (ex) {
  // handle error
}