(Java) Hashing Encoded Data

This example explains how it's important to know exactly what bytes are getting hashed when working with encoded data, such as hex, base64, etc.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

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

    CkCrypt2 crypt = new CkCrypt2();

    // Imagine we want to SHA-1 hash this A9133F6DC63E85BE0619763F8975CA076FF91B95CB6F121CD21C016143315E11B9ED4374F174B2CC
    String strToHash = "A9133F6DC63E85BE0619763F8975CA076FF91B95CB6F121CD21C016143315E11B9ED4374F174B2CC";

    // The question is:  Do we want to hash the bytes 0xA9, 0x13, 0x3F...
    // or do we want to literally hash each us-ascii byte:  'A', '9', '1', '3'.

    // The results will obviously be different depending on what bytes are actually hashed.

    // To hash the decoded bytes (i.e. 0xA9, 0x13, 0x3F...) we do this:

    // "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...
    crypt.put_Charset("hex");
    crypt.put_HashAlgorithm("sha1");
    // Get the hash result in lowercase hex
    crypt.put_EncodingMode("hex_lower");
    String hashValue = crypt.hashStringENC(strToHash);
    System.out.println("hash of decoded hex bytes: " + hashValue);

    // The result is 7a4a2ba73811fab98b4baaee2df164cbdd0d8e8e

    // This is how to hash the us-ascii byte values:
    // The Charset property defines the byte representation of the string passed to the hash algorithm:
    crypt.put_Charset("us-ascii");
    // The EncodingMode property defines the binary encoding (hex, base64, etc.) of the hash returned as an encoded string.
    crypt.put_EncodingMode("hex");
    crypt.put_HashAlgorithm("sha1");

    hashValue = crypt.hashStringENC(strToHash);
    System.out.println("hash of us-ascii bytes: " + hashValue);

    // The result is:  2A7500F88734F4B19C79852CA0FF3E1C561F31C8

    // 
  }
}