nodejs/doc/api/crypto.markdown

Crypto

Stability: 3 - Stable

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:

• pfx : A string or buffer holding the PFX or PKCS12 encoded private key, certificate and CA certificates
• key : A string holding the PEM encoded private key
• passphrase : A string of passphrase for the private key or pfx
• cert : A string holding the PEM encoded certificate
• ca : Either a string or list of strings of PEM encoded CA certificates to trust.
• crl : Either a string or list of strings of PEM encoded CRLs (Certificate Revocation List)
• ciphers: A string describing the ciphers to use or exclude. Consult http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT for details on the format.

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);
});

Class: Hash

The class for creating hash digests of data.

Returned by crypto.createHash.

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'. Defaults to 'binary'. This can be called many times with new data as it is streamed.

hash.digest([encoding])

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

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.

Class: Hmac

Class for creating cryptographic hmac content.

Returned by crypto.createHmac.

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])

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

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 a 'binary' encoded string or a buffer.

crypto.createCipheriv(algorithm, key, iv)

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

algorithm is the same as the argument to createCipher(). key is the raw key used by the algorithm. iv is an initialization vector.

key and iv must be 'binary' encoded strings or buffers.

Class: Cipher

Class for encrypting data.

Returned by crypto.createCipher and crypto.createCipheriv.

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

Updates the cipher with data, the encoding of which is given in input_encoding and can be 'utf8', 'ascii' or 'binary'. Defaults to 'binary'.

The output_encoding specifies the output format of the enciphered data, and can be 'binary', 'base64' or 'hex'. Defaults to 'binary'.

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

cipher.final([output_encoding])

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

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

cipher.setAutoPadding(auto_padding=true)

You can disable automatic padding of the input data to block size. If auto_padding is false, the length of the entire input data must be a multiple of the cipher's block size or final will fail. Useful for non-standard padding, e.g. using 0x0 instead of PKCS padding. You must call this before cipher.final.

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.

Class: Decipher

Class for decrypting data.

Returned by crypto.createDecipher and crypto.createDecipheriv.

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

Updates the decipher with data, which is encoded in 'binary', 'base64' or 'hex'. Defaults to 'binary'.

The output_decoding specifies in what format to return the deciphered plaintext: 'binary', 'ascii' or 'utf8'. Defaults to 'binary'.

decipher.final([output_encoding])

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

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

decipher.setAutoPadding(auto_padding=true)

You can disable auto padding if the data has been encrypted without standard block padding to prevent decipher.final from checking and removing it. Can only work if the input data's length is a multiple of the ciphers block size. You must call this before streaming data to decipher.update.

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'.

Class: Signer

Class for generating signatures.

Returned by crypto.createSign.

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])

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'. Defaults to 'binary'.

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.

Class: Verify

Class for verifying signatures.

Returned by crypto.createVerify.

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])

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'. Defaults to 'binary'.

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])

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

Class: DiffieHellman

The class for creating Diffie-Hellman key exchanges.

Returned by crypto.createDiffieHellman.

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'. Defaults to 'binary'.

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. Supplied key is interpreted using specified input_encoding, and secret is encoded using specified output_encoding. Encodings can be 'binary', 'hex', or 'base64'. The input encoding defaults to 'binary'. If no output encoding is given, the input encoding is used as output encoding.

diffieHellman.getPrime([encoding])

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

diffieHellman.getGenerator([encoding])

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

diffieHellman.getPublicKey([encoding])

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

diffieHellman.getPrivateKey([encoding])

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

diffieHellman.setPublicKey(public_key, [encoding])

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

diffieHellman.setPrivateKey(public_key, [encoding])

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

crypto.getDiffieHellman(group_name)

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

Example (obtaining a shared secret):

var crypto = require('crypto');
var alice = crypto.getDiffieHellman('modp5');
var bob = crypto.getDiffieHellman('modp5');

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

var alice_secret = alice.computeSecret(bob.getPublicKey(), 'binary', 'hex');
var bob_secret = bob.computeSecret(alice.getPublicKey(), 'binary', 'hex');

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

crypto.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).

crypto.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
}