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Crypto

Stability: 2 - Unstable; API changes are being discussed for
future versions.  Breaking changes will be minimized.  See below.

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

The crypto module 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.getCiphers()

Returns an array with the names of the supported ciphers.

Example:

var ciphers = crypto.getCiphers();
console.log(ciphers); // ['AES-128-CBC', 'AES-128-CBC-HMAC-SHA1', ...]

crypto.getHashes()

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

Example:

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

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.

It is a stream that is both readable and writable. The written data is used to compute the hash. Once the writable side of the stream is ended, use the read() method to get the computed hash digest. The legacy update and digest methods are also supported.

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'. If no encoding is provided and the input 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.

hash.digest([encoding])

Calculates the digest of all of the passed data to be hashed. The encoding can be 'hex', 'binary' or 'base64'. If no encoding is provided, then a buffer is returned.

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

crypto.createHmac(algorithm, key)

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

It is a stream that is both readable and writable. The written data is used to compute the hmac. Once the writable side of the stream is ended, use the read() method to get the computed digest. The legacy update and digest methods are also supported.

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'. If no encoding is provided, then a buffer is returned.

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

It is a stream that is both readable and writable. The written data is used to compute the hash. Once the writable side of the stream is ended, use the read() method to get the enciphered contents. The legacy update and final methods are also supported.

Note: createCipher derives keys with 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 you derive a key and iv yourself with crypto.pbkdf2 and to then use createCipheriv() to create the cipher stream.

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 objects are streams that are both readable and writable. The written plain text data is used to produce the encrypted data on the readable side. The legacy update and final methods are also supported.

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'. If no encoding is provided, then a buffer is expected. 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 no encoding is provided, then a buffer is returned.

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'. If no encoding is provided, then a buffer is returned.

Note: cipher object can not be used after final() method has 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 objects are streams that are both readable and writable. The written enciphered data is used to produce the plain-text data on the the readable side. The legacy update and final methods are also supported.

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

Updates the decipher with data, which is encoded in 'binary', 'base64' or 'hex'. If no encoding is provided, then a buffer is expected. If data is a Buffer then input_encoding is ignored.

The output_decoding specifies in what format to return the deciphered plaintext: 'binary', 'ascii' or 'utf8'. If no encoding is provided, then a buffer is returned.

decipher.final([output_encoding])

Returns any remaining plaintext which is deciphered, with output_encoding being one of: 'binary', 'ascii' or 'utf8'. If no encoding is provided, then a buffer is returned.

Note: decipher object can not be used after final() method has 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: Sign

Class for generating signatures.

Returned by crypto.createSign.

Sign objects are writable streams. The written data is used to generate the signature. Once all of the data has been written, the sign method will return the signature. The legacy update method is also supported.

sign.update(data)

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

sign.sign(private_key, [output_format])

Calculates the signature on all the updated data passed through the sign. 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'. If no encoding is provided, then a buffer is returned.

Note: sign object can not be used after sign() method has 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.

Verify objects are writable streams. The written data is used to validate against the supplied signature. Once all of the data has been written, the verify method will return true if the supplied signature is valid. The legacy update method is also supported.

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'. If no encoding is specified, then a buffer is expected.

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 has 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'. If no encoding is specified, then a buffer is expected.

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'. If no encoding is provided, then a buffer is returned.

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'. If the input encoding is not provided, then a buffer is expected.

If no output encoding is given, then a buffer is returned.

diffieHellman.getPrime([encoding])

Returns the Diffie-Hellman prime in the specified encoding, which can be 'binary', 'hex', or 'base64'. If no encoding is provided, then a buffer is returned.

diffieHellman.getGenerator([encoding])

Returns the Diffie-Hellman generator in the specified encoding, which can be 'binary', 'hex', or 'base64'. If no encoding is provided, then 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 no encoding is provided, then 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 no encoding is provided, then a buffer is returned.

diffieHellman.setPublicKey(public_key, [encoding])

Sets the Diffie-Hellman public key. Key encoding can be 'binary', 'hex' or 'base64'. If no encoding is provided, then a buffer is expected.

diffieHellman.setPrivateKey(private_key, [encoding])

Sets the Diffie-Hellman private key. Key encoding can be 'binary', 'hex' or 'base64'. If no encoding is provided, then a buffer is expected.

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(), null, 'hex');
var bob_secret = bob.computeSecret(alice.getPublicKey(), null, '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.pbkdf2Sync(password, salt, iterations, keylen)

Synchronous PBKDF2 function. Returns derivedKey or throws error.

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
  // most likely, entropy sources are drained
}

NOTE: Will throw error or invoke callback with error, if there is not enough accumulated entropy to generate cryptographically strong data. In other words, crypto.randomBytes without callback will not block even if all entropy sources are drained.

crypto.pseudoRandomBytes(size, [callback])

Generates non-cryptographically strong pseudo-random data. The data returned will be unique if it is sufficiently long, but is not necessarily unpredictable. For this reason, the output of this function should never be used where unpredictability is important, such as in the generation of encryption keys.

Usage is otherwise identical to crypto.randomBytes.

crypto.DEFAULT_ENCODING

The default encoding to use for functions that can take either strings or buffers. The default value is 'buffer', which makes it default to using Buffer objects. This is here to make the crypto module more easily compatible with legacy programs that expected 'binary' to be the default encoding.

Note that new programs will probably expect buffers, so only use this as a temporary measure.

Recent API Changes

The Crypto module was added to Node before there was the concept of a unified Stream API, and before there were Buffer objects for handling binary data.

As such, the streaming classes don't have the typical methods found on other Node classes, and many methods accepted and returned Binary-encoded strings by default rather than Buffers. This was changed to use Buffers by default instead.

This is a breaking change for some use cases, but not all.

For example, if you currently use the default arguments to the Sign class, and then pass the results to the Verify class, without ever inspecting the data, then it will continue to work as before. Where you once got a binary string and then presented the binary string to the Verify object, you'll now get a Buffer, and present the Buffer to the Verify object.

However, if you were doing things with the string data that will not work properly on Buffers (such as, concatenating them, storing in databases, etc.), or you are passing binary strings to the crypto functions without an encoding argument, then you will need to start providing encoding arguments to specify which encoding you'd like to use. To switch to the previous style of using binary strings by default, set the crypto.DEFAULT_ENCODING field to 'binary'. Note that new programs will probably expect buffers, so only use this as a temporary measure.