Visual FoxPro

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.

Visual FoxPro

LOCAL lnSuccess
LOCAL loSb
LOCAL i
LOCAL loCrypt
LOCAL lcIvHex
LOCAL lcKeyHex
LOCAL loBdEncrypted
LOCAL loSbOriginal

lnSuccess = 0

* 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('Chilkat.StringBuilder')
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('Chilkat.Crypt2')

* 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('Chilkat.BinData')
lnSuccess = loCrypt.EncryptSb(loSb,loBdEncrypted)
IF (lnSuccess <> 1) THEN
    ? loCrypt.LastErrorText
    RELEASE loSb
    RELEASE loCrypt
    RELEASE loBdEncrypted
    CANCEL
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('Chilkat.StringBuilder')
lnSuccess = loCrypt.DecryptSb(loBdEncrypted,loSbOriginal)
IF (lnSuccess <> 1) THEN
    ? loCrypt.LastErrorText
    RELEASE loSb
    RELEASE loCrypt
    RELEASE loBdEncrypted
    RELEASE loSbOriginal
    CANCEL
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.
lnSuccess = loCrypt.EncryptSb(loSb,loBdEncrypted)

* However.. DecryptSb appends the decrypted text to whatever may
* have already existed within sbOriginal.
lnSuccess = 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