Tcl

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.

Tcl

load ./chilkat.dll

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

set crypt [new_CkCrypt2]

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

set 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:
CkCrypt2_put_Charset $crypt "us-ascii"
# The EncodingMode property defines the binary encoding (hex, base64, etc.) of the hash returned as an encoded string.
CkCrypt2_put_EncodingMode $crypt "hex"
CkCrypt2_put_HashAlgorithm $crypt "sha256"

set hashValue [CkCrypt2_hashStringENC $crypt $strToHash]
puts [CkCrypt2_lastErrorText $crypt]
puts "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.
CkCrypt2_put_Charset $crypt "hex"
# The EncodingMode and HashAlgorithm remain the same..
set hashValue [CkCrypt2_hashStringENC $crypt $strToHash]
puts [CkCrypt2_lastErrorText $crypt]
puts "hash of 6 hex bytes: $hashValue"

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

delete_CkCrypt2 $crypt