(Visual FoxPro) Hash a Hex String

Demonstrates common pitfalls in hashing a hex string..

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

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loCrypt
LOCAL lcStrToHash
LOCAL lcHashValue

* This example assumes the Chilkat API to have been previously unlocked.
* See Global Unlock Sample for sample code.

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Crypt2')
loCrypt = CreateObject('Chilkat.Crypt2')

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

lcStrToHash = "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:
loCrypt.Charset = "us-ascii"
* The EncodingMode property defines the binary encoding (hex, base64, etc.) of the hash returned as an encoded string.
loCrypt.EncodingMode = "hex"
loCrypt.HashAlgorithm = "sha256"

lcHashValue = loCrypt.HashStringENC(lcStrToHash)
? loCrypt.LastErrorText
? "hash of 12 us-ascii bytes: " + lcHashValue

* 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.
loCrypt.Charset = "hex"
* The EncodingMode and HashAlgorithm remain the same..
lcHashValue = loCrypt.HashStringENC(lcStrToHash)
? loCrypt.LastErrorText
? "hash of 6 hex bytes: " + lcHashValue

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

RELEASE loCrypt