Generate a variable-length hash of `data` in Node.js

variableHash.js

var crypto = require("crypto");

/* variableHash - Generate a variable-length hash of `data`.

  Adapted node version 8.x
  ------------------------

  Similar to the answer here: http://crypto.stackexchange.com/a/3559/4829
  If you want a b-bit hash of the message m, then use the first b bits of AES-CTR(SHA256(m)).
  Rather than using the suggested algorithm in the stackexchange answer above, I developed
  my own.

  I decided to derive AES256 initialization vector and key from the output of SHA256(data).
  Then, the cipher is fed a zero-filled buffer as plaintext, which is encrypted using this key.
  The result should be a pseudorandom number generator seeded with a 256-bit hash of `data`.

  In other words, compute SHA256(m) and treat the resulting 256-bit string as a 256-bit AES key.
  Next, use AES in counter mode (with this key) to generate an unending stream of pseudorandom bits.
  Take the first b bits from this stream, and call it your hash.
    
*/

const IV = new Buffer('068f7bb47896981d6c8b3f9a186591ae', 'hex');
export function variableHash(data, size = 5, encoding = 'hex') {
        // Create zero-filled output buffer with specified byte size
        let output = Buffer.alloc(size);
        // Generate 256-bit hash of data
        let hash = crypto.createHash('sha256');
        hash.update(data);
        // Encrypt buffer using the SHA-256 hash as the AES-256 key
        let cipher = crypto.createCipheriv('aes256', hash.digest(), IV);
        let offset = output.write(cipher.update(output).toString('binary'));
        output.write(cipher.final().toString('binary'), offset);
        return output.toString(encoding);
}

I adapted the algorithm to work with node version 8.x.

Due to several breaking changes since the original code has been published, some non-trivial adaptions were necessary.