Visual FoxPro

Manually Duplicate SetSecretKeyViaPassword

Demonstrates how to duplicate the password string to binary secret key computation of SetSecretKeyViaPassword.

This is a cryptographically weak way of generating a secret key from a password. The SetSecretKeyViaPassword method is deprecated and should not be used.

Visual FoxPro

LOCAL loCrypt
LOCAL lcPassword
LOCAL loSb
LOCAL lcPasswordBase64

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

loCrypt = CreateObject('Chilkat.Crypt2')

* The password string is transformed to a binary secret key by computing the 
* MD5 digest (of the utf-8 password) to obtain 16 bytes.  
* If the KeyLength is greater than 16 bytes, then the MD5 digest of the Base64 encoding 
* of the utf-8 password is added.  A max of 32 bytes of key material is generated, and 
* this is truncated to the actual KeyLength required.

loCrypt.CryptAlgorithm = "aes"
loCrypt.KeyLength = 256

lcPassword = "this is my password"
loCrypt.SetSecretKeyViaPassword(lcPassword)

* Examine the resulting SecretKey in hex:
? "Computed Secret Key = " + loCrypt.GetEncodedKey("hex")

* Now perform the same computation manually:
loSb = CreateObject('Chilkat.StringBuilder')

loCrypt.HashAlgorithm = "md5"
loCrypt.Charset = "utf-8"
loCrypt.EncodingMode = "hex"
loSb.Append(loCrypt.HashStringENC(lcPassword))

lcPasswordBase64 = loCrypt.EncodeString(lcPassword,"utf-8","base64")
loSb.Append(loCrypt.HashStringENC(lcPasswordBase64))

? "Manually Computed = " + loSb.GetAsString()

* The output is:
* Computed Secret Key = 210D53992DFF432EC1B1A9698AF9DA16C7E90518F90E24828F78EC9E0A413B36
* Manually Computed = 210D53992DFF432EC1B1A9698AF9DA16C7E90518F90E24828F78EC9E0A413B36

RELEASE loCrypt
RELEASE loSb