(JavaScript) 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.
// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.
var crypt = new CkCrypt2();
// Imagine we want to SHA-1 hash this A9133F6DC63E85BE0619763F8975CA076FF91B95CB6F121CD21C016143315E11B9ED4374F174B2CC
var 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.Charset = "hex";
crypt.HashAlgorithm = "sha1";
// Get the hash result in lowercase hex
crypt.EncodingMode = "hex_lower";
var hashValue = crypt.HashStringENC(strToHash);
console.log("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.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 = "sha1";
hashValue = crypt.HashStringENC(strToHash);
console.log("hash of us-ascii bytes: " + hashValue);
// The result is: 2A7500F88734F4B19C79852CA0FF3E1C561F31C8
//
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