CkPython

Streaming Encryption by Encrypting in Chunks

See more Encryption Examples

Encrypt data in chunks. CkPython

import chilkat

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

crypt = chilkat.CkCrypt2()

crypt.put_CryptAlgorithm("aes")
crypt.put_CipherMode("cbc")
crypt.put_KeyLength(128)

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

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

sbEncrypted = chilkat.CkStringBuilder()

# 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.put_FirstChunk(True)
crypt.put_LastChunk(False)
sbEncrypted.Append(crypt.encryptStringENC(txt1))

# Encrypt the 2nd chunk
crypt.put_FirstChunk(False)
crypt.put_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.put_FirstChunk(False)
crypt.put_LastChunk(False)

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

# Now encrypt the last chunk:
crypt.put_FirstChunk(False)
crypt.put_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.put_FirstChunk(True)
crypt.put_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