(Chilkat2-Python) AES and CHACHA20 Encrypt/Decrypt Text

Demonstrates the use of the new EncryptSb and DecryptSb methods introduced in Chilkat v9.5.0.67 to encrypt/decrypt the contents of StringBuilder objects.

Note: This example requires Chilkat v9.5.0.67 or greater.

Chilkat2 Python Downloads install with pip pip3 install chilkat2 or download... Python Module for Windows, Linux, Alpine Linux, MacOS, Solaris

import sys
import chilkat2

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

# First build a string to be encrypted
sb = chilkat2.StringBuilder()
i = 1
while i < 10 :
    sb.AppendInt(i)
    sb.Append(" the quick brown fox jumped over the lazy dog.\r\n")
    i = i + 1

print(sb.GetAsString())

# The string to be encrypted looks like this:

# 1 the quick brown fox jumped over the lazy dog.
# 2 the quick brown fox jumped over the lazy dog.
# 3 the quick brown fox jumped over the lazy dog.
# 4 the quick brown fox jumped over the lazy dog.
# 5 the quick brown fox jumped over the lazy dog.
# 6 the quick brown fox jumped over the lazy dog.
# ...

crypt = chilkat2.Crypt2()

# Specify the encryption to be used.
# First we'll do AES-128 CBC
crypt.CryptAlgorithm = "aes"
crypt.CipherMode = "cbc"
crypt.KeyLength = 128

ivHex = "000102030405060708090A0B0C0D0E0F"
crypt.SetEncodedIV(ivHex,"hex")

keyHex = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F"
crypt.SetEncodedKey(keyHex,"hex")

# When EncryptSb is called, the contents of the source (sb)
# remains unmodified.  The encrypted bytes are written into bdEncrypted.
# If bdEncrypted already contained data, it is replaced with the encrypted bytes.
bdEncrypted = chilkat2.BinData()
success = crypt.EncryptSb(sb,bdEncrypted)
if (success != True):
    print(crypt.LastErrorText)
    sys.exit()

# Examine the encrypted bytes:
print(bdEncrypted.GetEncoded("base64_mime"))

# Sample encrypted data:

# 0DdNZ22ckMMJBiaKhAu3wUEfh16XW356NIUsDmNs/xwbHe/p1201OmpfzwXwKktkAefu2pckrBgC
# df+1w8lRo+KAy5n5wlAgMGM/UrsVJsp0BmDPk1vaxKrmrGpSXOVCQs1n2+0atIs5YLiOG+Va3+Mi
# EQNb4YK7bNMmvt0++irBxTiGnkx/RncfKwgkbBUpl2x7yV13MW6lapDT6Md0DKAMsTXFJYGeIdEf
# g2uxDDQzI5gUOUHTMrXQ8paD/K76KKB9Jpp/kAM9z8g/d8KUmuphA7KI64d38xsgOmcITlbhlCQ2
# PDkcU6RRzX0FUTUSMgQukhy0jkLZEjHX9poKJD+iJTOkcQUC3OqR9hKhSrvIgJN4lxdR71MheOoQ
# 2wmvRdq+agTWWh333Vmb6J6yDV79aSpnqEDrA8Ks7Xzciol0gve91+JtVJlJKjWwEzWEU8GxF7Q8
# eaWI70lsC5nTLGcbqgKu6gzkzHlHyHaE2FAQA/d5I2dvfsAYUQCza0Zdyw8mmTtHhlP2Tfxj1uPv
# H4Q7BGuKnx3SWT2CnpbX4091w7KzLAztrbFBo/Tf9w8ZpgTK9k1ryfW9/xnk6rW6iQ==

# Decrypt to restore back to the original:
sbOriginal = chilkat2.StringBuilder()
success = crypt.DecryptSb(bdEncrypted,sbOriginal)
if (success != True):
    print(crypt.LastErrorText)
    sys.exit()

# Examine the original data:
print(sbOriginal.GetAsString())

# ----------------------------------------------------------------------------------
# To do chacha20 encryption, just change the settings:

crypt.CryptAlgorithm = "chacha20"
crypt.KeyLength = 256
# The initial count is the initial block counter for the chacha20 algorithm.
# It can be any integer, but must be set to the same when decrypting.
crypt.InitialCount = 22

# EncryptSb completely replaces the contents of bdEncrypted.
success = crypt.EncryptSb(sb,bdEncrypted)

# However.. DecryptSb appends the decrypted text to whatever may
# have already existed within sbOriginal.
success = crypt.DecryptSb(bdEncrypted,sbOriginal)

print("----")
print("The original data should be here twice.  Once from the AES decrypt, and again from the chacha20 decrypt.")
print(sbOriginal.GetAsString())
print("Success.")