类: 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. The argument is the string name of the hash function to use. Sign objects are not to be created directly using the new keyword.

Example: Using Sign and [Verify][] objects as streams:

const crypto = require('crypto');

const { privateKey, publicKey } = crypto.generateKeyPairSync('ec', {
  namedCurve: 'sect239k1',
});

const sign = crypto.createSign('SHA256');
sign.write('some data to sign');
sign.end();
const signature = sign.sign(privateKey, 'hex');

const verify = crypto.createVerify('SHA256');
verify.write('some data to sign');
verify.end();
console.log(verify.verify(publicKey, signature, 'hex'));
// Prints: true

Example: Using the [sign.update()][] and [verify.update()][] methods:

const crypto = require('crypto');

const { privateKey, publicKey } = crypto.generateKeyPairSync('rsa', {
  modulusLength: 2048,
});

const sign = crypto.createSign('SHA256');
sign.update('some data to sign');
sign.end();
const signature = sign.sign(privateKey);

const verify = crypto.createVerify('SHA256');
verify.update('some data to sign');
verify.end();
console.log(verify.verify(publicKey, signature));
// Prints: true

sign.sign(privateKey[, outputEncoding])

• privateKey {Object | string | Buffer | KeyObject}
  • dsaEncoding {string}
  • padding {integer}
  • saltLength {integer}
• outputEncoding {string} The [encoding][] of the return value.
• Returns: {Buffer | string}

Calculates the signature on all the data passed through using either [sign.update()][] or [sign.write()][stream-writable-write].

If privateKey is not a [KeyObject][], this function behaves as if privateKey had been passed to [crypto.createPrivateKey()][]. If it is an object, the following additional properties can be passed:

• dsaEncoding {string} For DSA and ECDSA, this option specifies the format of the generated signature. It can be one of the following:

  • 'der' (default): DER-encoded ASN.1 signature structure encoding (r, s).
  • 'ieee-p1363': Signature format r || s as proposed in IEEE-P1363.

• padding {integer} Optional padding value for RSA, one of the following:

  • crypto.constants.RSA_PKCS1_PADDING (default)
  • crypto.constants.RSA_PKCS1_PSS_PADDING

  RSA_PKCS1_PSS_PADDING will use MGF1 with the same hash function used to sign the message as specified in section 3.1 of [RFC 4055][], unless an MGF1 hash function has been specified as part of the key in compliance with section 3.3 of [RFC 4055][].

• saltLength {integer} Salt length for when padding is RSA_PKCS1_PSS_PADDING. The special value crypto.constants.RSA_PSS_SALTLEN_DIGEST sets the salt length to the digest size, crypto.constants.RSA_PSS_SALTLEN_MAX_SIGN (default) sets it to the maximum permissible value.

If outputEncoding 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[, inputEncoding])

• data {string | Buffer | TypedArray | DataView}
• inputEncoding {string} The [encoding][] of the data string.

Updates the Sign content with the given data, the encoding of which is given in inputEncoding. If encoding is not provided, and the data is a string, an encoding of 'utf8' is enforced. If data is a [Buffer][], TypedArray, or DataView, then inputEncoding is ignored.

This can be called many times with new data as it is streamed.

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