DigestEngine Objects

DigestEngine objects are used to compute hash values for a given input based on different cryptographic hashing algorithms such as SHA-256.

To use DigestEngine objects, the crypto module must be imported.

Basic usage:

const crypto = require('crypto');

const sha256 = new crypto.DigestEngine('SHA256');
sha256.update('abc');
const hash = sha256.digest('hex');

Creating DigestEngine Objects

Use the DigestEngine constructor function to create a new DigestEngine object, passing as parameter the name of the hash algorithm to use. Most hash algorithms supported by the underlying OpenSSL implementation are supported. Algorithms that may need extra parameters are not supported. Examples are:

• MD5
• SHA1
• SHA256 or SHA2-256
• SHA384 or SHA2-384
• SHA512 or SHA2-512

DigestEngine Methods

update(data)

Updates the digest with the given data. The data may be given as a Buffer object or a string. Strings are encoded to UTF-8 before being passed to the hash function.

digest([encoding])

Finalizes computing the hash and returns the computed hash value. If no encoding is specified, the binary hash value is returned in a Buffer object. If an encoding is specified, the has value is returned as a string.

The following encoding values are supported:

• hex: The returned string contains the hash value in hexadecimal.
• base64: The returned string contains the hash value encoded using Base64 encoding.
• base64url: The returned string contains the has value encoding using Base64URL encoding.

Note that digest() must only be called once. Further calls will return invalid values. Furthermore, update() must not be called after digest(). The exception is that after calling reset(), the DigestEngine object can be used for a new digest computation.

reset()

Resets the digest object so that it can be used again to compute a new hash value.