(PowerBuilder) Example: Crypt2.RandomizeIV method

Demonstrates using a random initialization vector for AES GCM encryption.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

integer li_rc
oleobject loo_Crypt
string K
string ls_AAD
string ls_PT
string ls_IV
integer li_Success
string ls_CipherText
string ls_AuthTag
oleobject loo_BdEncrypted
string ls_ConcatenatedGcmOutput
oleobject loo_Decrypt
oleobject loo_BdFromEncryptor
integer li_Sz
string ls_ExtractedIV
string ls_ExtractedCipherText
string ls_ExpectedAuthTag
string ls_DecryptedText

// This example assumes 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 = "gcm"
loo_Crypt.KeyLength = 256

K = "000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F"
ls_AAD = "feedfacedeadbeeffeedfacedeadbeefabaddad2"
ls_PT = "This is the text to be AES-GCM encrypted."

// Generate a random IV.
loo_Crypt.RandomizeIV()
ls_IV = loo_Crypt.GetEncodedIV("hex")

loo_Crypt.SetEncodedKey(K,"hex")

li_Success = loo_Crypt.SetEncodedAad(ls_AAD,"hex")

// Return the encrypted bytes as base64
loo_Crypt.EncodingMode = "base64"
loo_Crypt.Charset = "utf-8"
ls_CipherText = loo_Crypt.EncryptStringENC(ls_PT)
if loo_Crypt.LastMethodSuccess <> 1 then
    Write-Debug loo_Crypt.LastErrorText
    destroy loo_Crypt
    return
end if

// Get the GCM authenticated tag computed when encrypting.
ls_AuthTag = loo_Crypt.GetEncodedAuthTag("base64")

Write-Debug "Cipher Text: " + ls_CipherText
Write-Debug "Auth Tag: " + ls_AuthTag

// Let's send the IV, CipherText, and AuthTag to the decrypting party.
// We'll send them concatenated like this: [IV || Ciphertext || AuthTag]
// In base64 format.
loo_BdEncrypted = create oleobject
li_rc = loo_BdEncrypted.ConnectToNewObject("Chilkat.BinData")

loo_BdEncrypted.AppendEncoded(ls_IV,"hex")
loo_BdEncrypted.AppendEncoded(ls_CipherText,"base64")
loo_BdEncrypted.AppendEncoded(ls_AuthTag,"base64")

ls_ConcatenatedGcmOutput = loo_BdEncrypted.GetEncoded("base64")
Write-Debug "Concatenated GCM Output: " + ls_ConcatenatedGcmOutput

// Sample output so far:

// -------------------------------------------------------------------------------------
// Now let's GCM decrypt...
// -------------------------------------------------------------------------------------

loo_Decrypt = create oleobject
li_rc = loo_Decrypt.ConnectToNewObject("Chilkat.Crypt2")

// The values shared and agreed upon by both sides beforehand are: algorithm, cipher mode, secret key, and AAD.
// Sometimes the IV can be a value already known and agreed upon, but in this case the encryptor sends the IV to the decryptor.
loo_Decrypt.CryptAlgorithm = "aes"
loo_Decrypt.CipherMode = "gcm"
loo_Decrypt.KeyLength = 256
loo_Decrypt.SetEncodedKey(K,"hex")
loo_Decrypt.SetEncodedAad(ls_AAD,"hex")

loo_BdFromEncryptor = create oleobject
li_rc = loo_BdFromEncryptor.ConnectToNewObject("Chilkat.BinData")

loo_BdFromEncryptor.AppendEncoded(ls_ConcatenatedGcmOutput,"base64")

li_Sz = loo_BdFromEncryptor.NumBytes

// Extract the parts.
ls_ExtractedIV = loo_BdFromEncryptor.GetEncodedChunk(0,16,"hex")
ls_ExtractedCipherText = loo_BdFromEncryptor.GetEncodedChunk(16,li_Sz - 32,"base64")
ls_ExpectedAuthTag = loo_BdFromEncryptor.GetEncodedChunk(li_Sz - 16,16,"base64")

// Before GCM decrypting, we must set the authenticated tag to the value that is expected.
// The decryption will fail if the resulting authenticated tag is not equal to the expected result.
li_Success = loo_Decrypt.SetEncodedAuthTag(ls_ExpectedAuthTag,"base64")

// Also set the IV.
loo_Decrypt.SetEncodedIV(ls_ExtractedIV,"hex")

// Decrypt..
loo_Decrypt.EncodingMode = "base64"
loo_Decrypt.Charset = "utf-8"
ls_DecryptedText = loo_Decrypt.DecryptStringENC(ls_ExtractedCipherText)
if loo_Decrypt.LastMethodSuccess <> 1 then
    // Failed.  The resultant authenticated tag did not equal the expected authentication tag.
    Write-Debug loo_Decrypt.LastErrorText
    destroy loo_Crypt
    destroy loo_BdEncrypted
    destroy loo_Decrypt
    destroy loo_BdFromEncryptor
    return
end if

Write-Debug "Decrypted: " + ls_DecryptedText


destroy loo_Crypt
destroy loo_BdEncrypted
destroy loo_Decrypt
destroy loo_BdFromEncryptor