PowerBuilder

Encrypting a Data Stream

See more Encryption Examples

This example illustrates encrypting a large dataset using symmetric encryption algorithms like AES, ChaCha20, Blowfish, etc. The data is processed in chunks using the EncryptStringENC method. The FirstChunk and LastChunk properties identify whether a chunk is the first, intermediate, or last in the encrypted stream. By default, both properties are set to _TRUE_, indicating that the data provided represents the entire dataset.

You can provide data chunks smaller than the encryption algorithm's block size. For example, AES uses 16-byte blocks; 3DES, and Blowfish use 8-byte blocks; and ChaCha20, as a streaming algorithm, effectively has a block size of 1 byte.

Chilkat handles the buffering of data as needed. If a data chunk smaller than the block size is provided, an empty string (or 0 bytes) is returned, and the data is buffered to be combined with subsequent chunks. The final chunk is padded to the algorithm's block size (as determined by the PaddingScheme property) to complete the encryption process.

Chunk-wise decryption follows the same procedure as chunk-wise encryption.

PowerBuilder

integer li_rc
oleobject loo_Crypt
string ls_Txt1
string ls_Txt2
string ls_Txt3
oleobject loo_SbEncrypted
integer i
string ls_DecryptedText

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

loo_Crypt = create oleobject
li_rc = loo_Crypt.ConnectToNewObject("Chilkat.Crypt2")
if li_rc < 0 then
    destroy loo_Crypt
    MessageBox("Error","Connecting to COM object failed")
    return
end if

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

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

loo_Crypt.EncodingMode = "hex"
ls_Txt1 = "The quick brown fox jumped over the lazy dog.~r~n"
ls_Txt2 = "-~r~n"
ls_Txt3 = "Done.~r~n"

loo_SbEncrypted = create oleobject
li_rc = loo_SbEncrypted.ConnectToNewObject("Chilkat.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.)
loo_Crypt.FirstChunk = 1
loo_Crypt.LastChunk = 0
loo_SbEncrypted.Append(loo_Crypt.EncryptStringENC(ls_Txt1))

// Encrypt the 2nd chunk
loo_Crypt.FirstChunk = 0
loo_Crypt.LastChunk = 0
loo_SbEncrypted.Append(loo_Crypt.EncryptStringENC(ls_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...
loo_Crypt.FirstChunk = 0
loo_Crypt.LastChunk = 0

for i = 0 to 4
    loo_SbEncrypted.Append(loo_Crypt.EncryptStringENC(ls_Txt1))
    loo_SbEncrypted.Append(loo_Crypt.EncryptStringENC(ls_Txt2))
next

// Now encrypt the last chunk:
loo_Crypt.FirstChunk = 0
loo_Crypt.LastChunk = 1
loo_SbEncrypted.Append(loo_Crypt.EncryptStringENC(ls_Txt3))

Write-Debug loo_SbEncrypted.GetAsString()

// Now decrypt in one call.
// (The data we're decrypting is both the first AND last chunk.)  
loo_Crypt.FirstChunk = 1
loo_Crypt.LastChunk = 1
ls_DecryptedText = loo_Crypt.DecryptStringENC(loo_SbEncrypted.GetAsString())

Write-Debug ls_DecryptedText

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


destroy loo_Crypt
destroy loo_SbEncrypted