Tcl

AES XTS Mode

See more Encryption Examples

Demonstrates the AES-XTS mode of operation.

Note: This example requires Chilkat v9.5.0.91 or greater.

Tcl

load ./chilkat.dll

set success 0

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

# Here we have a sample from CAVS validatition data:

# COUNT = 301
# DataUnitLen = 200
# Key = 
# 394c97881abd989d29c703e48a72b397
# a7acf51b59649eeea9b33274d8541df4
# i = 4b15c684a152d485fe9937d39b168c29
# PT = 2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0
# CT = f3473802e38a3ffef4d4fb8e6aa266ebde553a64528a06463e

# Note: The above sample requires an AES-XTS implementation that fully supports ciphertext-stealing
# because the data to be encrypted is not an even multiple of the AES block size (i.e. not a multiple of 16 bytes).
# Chilkat fully supports AES-XTS with ciphertext stealing.
# (i.e. Chilkat implements XEX-based tweaked-codebook mode with ciphertext stealing (XTS))

set key "394c97881abd989d29c703e48a72b397"
set tweakKey "a7acf51b59649eeea9b33274d8541df4"
set dataUnit "4b15c684a152d485fe9937d39b168c29"

set bd [new_CkBinData]

CkBinData_AppendEncoded $bd "2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0" "hex"

set crypt [new_CkCrypt2]

CkCrypt2_put_CryptAlgorithm $crypt "aes"
CkCrypt2_put_CipherMode $crypt "xts"
CkCrypt2_put_KeyLength $crypt 128

CkCrypt2_SetEncodedKey $crypt $key "hex"
CkCrypt2_XtsSetEncodedTweakKey $crypt $tweakKey "hex"
CkCrypt2_XtsSetEncodedTweakValue $crypt $dataUnit "hex"

# In-place encrypt the contents of bd.
set success [CkCrypt2_EncryptBd $crypt $bd]

puts "CT = [CkBinData_getEncoded $bd hexlower]"

# Decrypt to revert back to the unencrypted content:
set success [CkCrypt2_DecryptBd $crypt $bd]

puts "PT = [CkBinData_getEncoded $bd hexlower]"

# Output:
# CT = f3473802e38a3ffef4d4fb8e6aa266ebde553a64528a06463e
# PT = 2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0

delete_CkBinData $bd
delete_CkCrypt2 $crypt