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doc: improve Sign/Verify examples and docs
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- Use complete examples that can be pasted and run as-is
- Move note about algorithm to the functions it applies to
- Uncapitalize inconsistence use of "Class"
- Use both EC and RSA keys in the examples
- Note that hash and digest are two names for the same algorithms

PR-URL: #25452
Reviewed-By: Vse Mozhet Byt <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>
Reviewed-By: James M Snell <[email protected]>
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@sam-github @addaleax
sam-github authored and addaleax committed Jan 15, 2019
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Showing 1 changed file with 45 additions and 64 deletions.
109 changes: 45 additions & 64 deletions doc/api/crypto.md
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Original file line number Diff line number Diff line change
Expand Up @@ -1018,7 +1018,7 @@ This can be called many times with new data as it is streamed.
added: v0.1.94
-->

The `Hmac` Class is a utility for creating cryptographic HMAC digests. It can
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
Expand Down Expand Up @@ -1196,7 +1196,7 @@ or `'private'` for private (asymmetric) keys.
added: v0.1.92
-->

The `Sign` Class is a utility for generating signatures. It can be used in one
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
Expand All @@ -1208,51 +1208,46 @@ 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` objects as streams:
Example: Using `Sign` and [`Verify`][] objects as streams:

```js
const crypto = require('crypto');
const sign = crypto.createSign('SHA256');

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 privateKey = getPrivateKeySomehow();
console.log(sign.sign(privateKey, 'hex'));
// Prints: the calculated signature using the specified private key and
// SHA-256. For RSA keys, the algorithm is RSASSA-PKCS1-v1_5 (see padding
// parameter below for RSASSA-PSS). For EC keys, the algorithm is ECDSA.
const verify = crypto.createVerify('SHA256');
verify.write('some data to sign');
verify.end();
console.log(verify.verify(publicKey, signature));
// Prints: true or false
```

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

```js
const crypto = require('crypto');
const sign = crypto.createSign('SHA256');

sign.update('some data to sign');

const privateKey = getPrivateKeySomehow();
console.log(sign.sign(privateKey, 'hex'));
// Prints: the calculated signature
```

In some cases, a `Sign` instance can also be created by passing in a signature
algorithm name, such as 'RSA-SHA256'. This will use the corresponding digest
algorithm. This does not work for all signature algorithms, such as
'ecdsa-with-SHA256'. Use digest names instead.

Example: signing using legacy signature algorithm name

```js
const crypto = require('crypto');
const sign = crypto.createSign('RSA-SHA256');
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 privateKey = getPrivateKeySomehow();
console.log(sign.sign(privateKey, 'hex'));
// Prints: the calculated signature
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])
Expand Down Expand Up @@ -1332,34 +1327,7 @@ of two ways:
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:

```js
const crypto = require('crypto');
const verify = crypto.createVerify('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:

```js
const crypto = require('crypto');
const verify = crypto.createVerify('SHA256');

verify.update('some data to sign');

const publicKey = getPublicKeySomehow();
const signature = getSignatureToVerify();
console.log(verify.verify(publicKey, signature));
// Prints: true or false
```
See [`Sign`][] for examples.

### verify.update(data[, inputEncoding])
<!-- YAML
Expand Down Expand Up @@ -1886,10 +1854,15 @@ added: v0.1.92
* `options` {Object} [`stream.Writable` options][]
* Returns: {Sign}

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. Optional `options` argument controls the
`stream.Writable` behavior.
Creates and returns a `Sign` object that uses the given `algorithm`. Use
[`crypto.getHashes()`][] to obtain the names of the available digest algorithms.
Optional `options` argument controls the `stream.Writable` behavior.

In some cases, a `Sign` instance can be created using the name of a signature
algorithm, such as `'RSA-SHA256'`, instead of a digest algorithm. This will use
the corresponding digest algorithm. This does not work for all signature
algorithms, such as `'ecdsa-with-SHA256'`, so it is best to always use digest
algorithm names.

### crypto.createVerify(algorithm[, options])
<!-- YAML
Expand All @@ -1904,6 +1877,12 @@ Use [`crypto.getHashes()`][] to obtain an array of names of the available
signing algorithms. Optional `options` argument controls the
`stream.Writable` behavior.

In some cases, a `Verify` instance can be created using the name of a signature
algorithm, such as `'RSA-SHA256'`, instead of a digest algorithm. This will use
the corresponding digest algorithm. This does not work for all signature
algorithms, such as `'ecdsa-with-SHA256'`, so it is best to always use digest
algorithm names.

### crypto.generateKeyPair(type, options, callback)
<!-- YAML
added: v10.12.0
Expand Down Expand Up @@ -2084,7 +2063,7 @@ added: v10.0.0
added: v0.9.3
-->
* Returns: {string[]} An array of the names of the supported hash algorithms,
such as `'RSA-SHA256'`.
such as `'RSA-SHA256'`. Hash algorithms are also called "digest" algorithms.

```js
const hashes = crypto.getHashes();
Expand Down Expand Up @@ -3103,7 +3082,9 @@ the `crypto`, `tls`, and `https` modules and are generally specific to OpenSSL.
[`Buffer`]: buffer.html
[`EVP_BytesToKey`]: https://www.openssl.org/docs/man1.1.0/crypto/EVP_BytesToKey.html
[`KeyObject`]: #crypto_class_keyobject
[`Sign`]: #crypto_class_sign
[`UV_THREADPOOL_SIZE`]: cli.html#cli_uv_threadpool_size_size
[`Verify`]: #crypto_class_verify
[`cipher.final()`]: #crypto_cipher_final_outputencoding
[`cipher.update()`]: #crypto_cipher_update_data_inputencoding_outputencoding
[`crypto.createCipher()`]: #crypto_crypto_createcipher_algorithm_password_options
Expand Down

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