Chilkat2-Python

Streaming Encryption by Encrypting in Chunks

See more Encryption Examples

Encrypt data in chunks. Chilkat2-Python

import chilkat2

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

crypt = chilkat2.Crypt2()

crypt.CryptAlgorithm = "aes"
crypt.CipherMode = "cbc"
crypt.KeyLength = 128

crypt.SetEncodedKey("000102030405060708090A0B0C0D0E0F","hex")
crypt.SetEncodedIV("000102030405060708090A0B0C0D0E0F","hex")

crypt.EncodingMode = "hex"
txt1 = "The quick brown fox jumped over the lazy dog.\r\n"
txt2 = "-\r\n"
txt3 = "Done.\r\n"

sbEncrypted = chilkat2.StringBuilder()

# Encrypt the 1st chunk:
# (don't worry about feeding the data to the encryptor in 
# exact multiples of the encryption algorithm's block size.
# Chilkat will buffer the data.)
crypt.FirstChunk = True
crypt.LastChunk = False
sbEncrypted.Append(crypt.EncryptStringENC(txt1))

# Encrypt the 2nd chunk
crypt.FirstChunk = False
crypt.LastChunk = False
sbEncrypted.Append(crypt.EncryptStringENC(txt2))

# Now encrypt N more chunks...
# Remember -- we're doing this in CBC mode, so each call
# to the encrypt method depends on the state from previous
# calls...
crypt.FirstChunk = False
crypt.LastChunk = False

for i in range(0,5):
    sbEncrypted.Append(crypt.EncryptStringENC(txt1))
    sbEncrypted.Append(crypt.EncryptStringENC(txt2))

# Now encrypt the last chunk:
crypt.FirstChunk = False
crypt.LastChunk = True
sbEncrypted.Append(crypt.EncryptStringENC(txt3))

print(sbEncrypted.GetAsString())

# Now decrypt in one call.
# (The data we're decrypting is both the first AND last chunk.)  
crypt.FirstChunk = True
crypt.LastChunk = True
decryptedText = crypt.DecryptStringENC(sbEncrypted.GetAsString())

print(decryptedText)

# Note: You may decrypt in N chunks by setting the FirstChunk
# and LastChunk properties prior to calling the Decrypt* methods