Dart

Hash a Hex String

See more Encryption Examples

Demonstrates common pitfalls in hashing a hex string..

Note: This example requires Chilkat v9.5.0.70 or greater.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example assumes the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  final crypt = CkCrypt2();

  // We have a hex string to be SHA-256 hashed:  "b08538d832bf"
  // The result we expect to receive is "8a9f04cb1adfbd7f59c5918635f92f6c847e5b15f9828519d2fdbd6ead0918fc"

  final strToHash = 'b08538d832bf';

  // How do we get this result?

  // The 1st question to be answered is:  What bytes are getting hashed?  
  // There are two possibilities:
  // 1) Hash 12 bytes, namely the us-ascii values for 'b', '0', '8', '5', .... 'b', 'f'
  // or
  // 2) Hash 6 bytes:  0xb0, 0x85, ... 0xbf
  // 

  // This is how to hash the 12 us-ascii byte values:
  // The Charset property defines the byte representation of the string passed to the hash algorithm:
  crypt.charset = 'us-ascii';
  // The EncodingMode property defines the binary encoding (hex, base64, etc.) of the hash returned as an encoded string.
  crypt.encodingMode = 'hex';
  crypt.hashAlgorithm = 'sha256';

  var hashValue = crypt.hashStringENC(strToHash);
  print(crypt.lastErrorText);
  print('hash of 12 us-ascii bytes: $hashValue');

  // The result is:  327F2B33A0F0580D09840B0D7CEE54514CA33E9A  (not what we were hoping).

  // -------------------------------------------
  // This is how to hash the 6 bytes
  // 
  // "hex" is not an actual character encoding.  It's a special value to be used to tell Chilkat to hex decode
  // the string and pass the decoded bytes to the hash algorithm...
  // Note: This example requires Chilkat v9.5.0.70 or greater for the "hex" Charset to work properly.
  crypt.charset = 'hex';
  // The EncodingMode and HashAlgorithm remain the same..
  hashValue = crypt.hashStringENC(strToHash);
  print(crypt.lastErrorText);
  print('hash of 6 hex bytes: $hashValue');

  // The result is 8A9F04CB1ADFBD7F59C5918635F92F6C847E5B15F9828519D2FDBD6EAD0918FC (which equals the hash we were expecting)
}