code: function sha512half(buffer) {
    var sha512 = createHash('sha512');
    return sha512.update(buffer).digest('hex').toUpperCase().slice(0, 64);
  }
docs: For a hash function, rippled uses SHA-512 and then truncates the result to the first 256 bytes. This algorithm, informally called SHA-512Half, provides an output that has comparable security to SHA-256, but runs faster on 64-bit processors.