Lianja

AES and CHACHA20 Encrypt/Decrypt Text

See more Encryption Examples

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.

Lianja

llSuccess = .F.

// 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
loSb = createobject("CkStringBuilder")
i = 1
do while i < 10
    loSb.AppendInt(i)
    loSb.Append(" the quick brown fox jumped over the lazy dog." + Chr(13) + Chr(10))
    i = i + 1
enddo

? loSb.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.
// ...

loCrypt = createobject("CkCrypt2")

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

lcIvHex = "000102030405060708090A0B0C0D0E0F"
loCrypt.SetEncodedIV(lcIvHex,"hex")

lcKeyHex = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F"
loCrypt.SetEncodedKey(lcKeyHex,"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.
loBdEncrypted = createobject("CkBinData")
llSuccess = loCrypt.EncryptSb(loSb,loBdEncrypted)
if (llSuccess <> .T.) then
    ? loCrypt.LastErrorText
    release loSb
    release loCrypt
    release loBdEncrypted
    return
endif

// Examine the encrypted bytes:
? loBdEncrypted.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:
loSbOriginal = createobject("CkStringBuilder")
llSuccess = loCrypt.DecryptSb(loBdEncrypted,loSbOriginal)
if (llSuccess <> .T.) then
    ? loCrypt.LastErrorText
    release loSb
    release loCrypt
    release loBdEncrypted
    release loSbOriginal
    return
endif

// Examine the original data:
? loSbOriginal.GetAsString()

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

loCrypt.CryptAlgorithm = "chacha20"
loCrypt.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.
loCrypt.InitialCount = 22

// EncryptSb completely replaces the contents of bdEncrypted.
llSuccess = loCrypt.EncryptSb(loSb,loBdEncrypted)

// However.. DecryptSb appends the decrypted text to whatever may
// have already existed within sbOriginal.
llSuccess = loCrypt.DecryptSb(loBdEncrypted,loSbOriginal)

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


release loSb
release loCrypt
release loBdEncrypted
release loSbOriginal