Crypto | Node.js v7.10.1 Documentation (original) (raw)

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 thecrypto module. In such cases, calling require('crypto') will result in an error being thrown.

let 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. Thecertificate.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. Thecertificate.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');

let encrypted = '';
cipher.on('readable', () => {
  const 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');

let 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_encodingparameter 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])#

Updates the cipher with data. If the input_encoding argument is given, its value must be one of 'utf8', 'ascii', or 'latin1' and the dataargument is a string using the specified encoding. If the input_encodingargument is not given, data must be a Buffer. If data is aBuffer 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_encodingis specified, a string using the specified encoding is returned. If nooutput_encoding is provided, a Buffer is returned.

The cipher.update() method can be called multiple times with new data untilcipher.final() is called. Calling cipher.update() aftercipher.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');

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

const 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');

const encrypted = 'ca981be48e90867604588e75d04feabb63cc007a8f8ad89b10616ed84d815504';
let 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_encodingparameter 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)#

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)#

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, callingdecipher.setAutoPadding(false) will disable automatic padding to preventdecipher.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 beforedecipher.update().

Returns this for method chaining.

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

Updates the decipher with data. If the input_encoding argument is given, its value must be one of 'latin1', 'base64', or 'hex' and the dataargument is a string using the specified encoding. If the input_encodingargument is not given, data must be a Buffer. If data is aBuffer 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_encodingis specified, a string using the specified encoding is returned. If nooutput_encoding is provided, a Buffer is returned.

The decipher.update() method can be called multiple times with new data untildecipher.final() is called. Calling decipher.update() afterdecipher.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 thecrypto.createDiffieHellman() function.

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

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

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

// Exchange and generate the secret...
const aliceSecret = alice.computeSecret(bobKey);
const bobSecret = bob.computeSecret(aliceKey);

// OK
assert.strictEqual(aliceSecret.toString('hex'), bobSecret.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, aBuffer 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 aBuffer 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 constantsmodule):

• 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 thecrypto.createECDH() function.

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

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

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

// Exchange and generate the secret...
const aliceSecret = alice.computeSecret(bobKey);
const bobSecret = bob.computeSecret(aliceKey);

assert.strictEqual(aliceSecret.toString('hex'), bobSecret.toString('hex'));
  // 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'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 aBuffer 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'. Ifencoding is provided a string is returned; otherwise a Bufferis 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 andformat.

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'. Ifencoding 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. Ifprivate_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: v0.11.14Deprecated 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 ECDHonly requires a private key and the other party's public key to compute the shared secret. Typically either ecdh.generateKeys() orecdh.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 aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');
const bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');

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

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. Hashobjects 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', () => {
  const 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 thehash.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])#

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 theninput_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. Hmacobjects 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', () => {
  const 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])#

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 theninput_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 thesign.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. Signobjects 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 privateKey = getPrivateKeySomehow();
console.log(sign.sign(privateKey, '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 privateKey = getPrivateKeySomehow();
console.log(sign.sign(privateKey, '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 privateKey =
`-----BEGIN EC PRIVATE KEY-----
MHcCAQEEIF+jnWY1D5kbVYDNvxxo/Y+ku2uJPDwS0r/VuPZQrjjVoAoGCCqGSM49
AwEHoUQDQgAEurOxfSxmqIRYzJVagdZfMMSjRNNhB8i3mXyIMq704m2m52FdfKZ2
pQhByd5eyj3lgZ7m7jbchtdgyOF8Io/1ng==
-----END EC PRIVATE KEY-----`;

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

sign.sign(private_key[, output_format])#

Added in: v0.1.92

Calculates the signature on all the data passed through using eithersign.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: - PEM encoded private key
• passphrase: - passphrase for the private key

The output_format can specify one of 'latin1', 'hex' or 'base64'. Ifoutput_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])#

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

verifier.update(data[, input_encoding])#

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 theninput_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 inCrypto 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 andpassword.

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 ofEVP_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 aninitialization vector. Both arguments must be 'utf8' encoded strings orbuffers.

crypto.createCredentials(details)#

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

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

• details 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 withtls.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 andpassword (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 ofEVP_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, keyand 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 aninitialization vector. Both arguments must be 'utf8' encoded strings orbuffers.

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

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. Ifgenerator 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 ofprime_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. Usecrypto.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', () => {
  const 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', () => {
  const 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); // ['Oakley-EC2N-3', 'Oakley-EC2N-4', ...]

crypto.getDiffieHellman(group_name)#

Added in: v0.7.5

Creates a predefined DiffieHellman key exchange object. The supported groups are: 'modp1', 'modp2', 'modp5' (defined inRFC 2412, but see Caveats) and 'modp14', 'modp15','modp16', 'modp17', 'modp18' (defined in RFC 3526). The returned object mimics the interface of objects created bycrypto.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 aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');
const bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');

/* aliceSecret and bobSecret should be the same */
console.log(aliceSecret === bobSecret);

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); // ['DSA', 'DSA-SHA', 'DSA-SHA1', ...]

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

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 thepassword, salt and iterations.

The supplied callback function is called with two arguments: err andderivedKey. 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. SeeNIST 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'));  // '3745e48...aa39b34'
});

An array of supported digest functions can be retrieved usingcrypto.getHashes().

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

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 thepassword, 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. SeeNIST SP 800-132 for details.

Example:

const crypto = require('crypto');
const key = crypto.pbkdf2Sync('secret', 'salt', 100000, 512, 'sha512');
console.log(key.toString('hex'));  // '3745e48...aa39b34'

An array of supported digest functions can be retrieved usingcrypto.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: - PEM encoded private key
• passphrase: - 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.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: - PEM encoded private key
• passphrase: - 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: - PEM encoded public key
• passphrase: - 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: - PEM encoded public key
• passphrase: - 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. Thebuf 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.randomFillSync(buffer[, offset][, size])#

Added in: v7.10.0

• buffer | Must be supplied.
• offset Defaults to 0.
• size Defaults to buffer.length - offset.

Synchronous version of crypto.randomFill().

Returns buffer

const buf = Buffer.alloc(10);
console.log(crypto.randomFillSync(buf).toString('hex'));

crypto.randomFillSync(buf, 5);
console.log(buf.toString('hex'));

// The above is equivalent to the following:
crypto.randomFillSync(buf, 5, 5);
console.log(buf.toString('hex'));

crypto.randomFill(buffer[, offset][, size], callback)#

Added in: v7.10.0

• buffer | Must be supplied.
• offset Defaults to 0.
• size Defaults to buffer.length - offset.
• callback function(err, buf) {}.

This function is similar to crypto.randomBytes() but requires the first argument to be a Buffer that will be filled. It also requires that a callback is passed in.

If the callback function is not provided, an error will be thrown.

const buf = Buffer.alloc(10);
crypto.randomFill(buf, (err, buf) => {
  if (err) throw err;
  console.log(buf.toString('hex'));
});

crypto.randomFill(buf, 5, (err, buf) => {
  if (err) throw err;
  console.log(buf.toString('hex'));
});

// The above is equivalent to the following:
crypto.randomFill(buf, 5, 5, (err, buf) => {
  if (err) throw err;
  console.log(buf.toString('hex'));
});

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 flagsis a bit field taking one of or a mix of the following flags (defined incrypto.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

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 orcapability urls.

a and b must both be Buffers, 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.

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 streamsAPI (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#

OpenSSL Engine Constants#

Other OpenSSL Constants#

Node.js Crypto Constants#