(Visual FoxPro) JWE with Binary Data

Demonstrates how to create a JWE that contains a binary payload (such as a JPG image).

Note: This example requires Chilkat v9.5.0.66 or greater.

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

LOCAL lnSuccess
LOCAL loJpgBytes
LOCAL loJwe
LOCAL loJweProtHdr
LOCAL lcAesWrappingKey
LOCAL loSbJwe
LOCAL loJwe2
LOCAL loJpgOriginal

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

* Note: This example requires Chilkat v9.5.0.66 or greater.

* Load a JPG file that will be the JWE payload.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loJpgBytes = CreateObject('Chilkat.BinData')
lnSuccess = loJpgBytes.LoadFile("qa_data/jpg/starfish.jpg")
* Make sure your app checks the success/failure of the call to LoadFile..
? "Original JPG size = " + STR(loJpgBytes.NumBytes)

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Jwe')
loJwe = CreateObject('Chilkat.Jwe')

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJweProtHdr = CreateObject('Chilkat.JsonObject')
loJweProtHdr.AppendString("alg","A128KW")
loJweProtHdr.AppendString("enc","A128CBC-HS256")
loJwe.SetProtectedHeader(loJweProtHdr)

lcAesWrappingKey = "GawgguFyGrWKav7AX4VKUg"
loJwe.SetWrappingKey(0,lcAesWrappingKey,"base64url")

* Encrypt and return the JWE in sbJwe:
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSbJwe = CreateObject('Chilkat.StringBuilder')
lnSuccess = loJwe.EncryptBd(loJpgBytes,loSbJwe)
IF (lnSuccess <> 1) THEN
    ? loJwe.LastErrorText
    RELEASE loJpgBytes
    RELEASE loJwe
    RELEASE loJweProtHdr
    RELEASE loSbJwe
    CANCEL
ENDIF

* Show the JWE:
? loSbJwe.GetAsString()
? "size of JWE: " + STR(loSbJwe.Length)

* ---------------------------------------------------------
* Decrypt to get the original JPG file..

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Jwe')
loJwe2 = CreateObject('Chilkat.Jwe')
lnSuccess = loJwe2.LoadJweSb(loSbJwe)
IF (lnSuccess <> 1) THEN
    ? loJwe2.LastErrorText
    RELEASE loJpgBytes
    RELEASE loJwe
    RELEASE loJweProtHdr
    RELEASE loSbJwe
    RELEASE loJwe2
    CANCEL
ENDIF

* Set the AES wrap key.
loJwe2.SetWrappingKey(0,lcAesWrappingKey,"base64url")

* Decrypt.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loJpgOriginal = CreateObject('Chilkat.BinData')
lnSuccess = loJwe2.DecryptBd(0,loJpgOriginal)
IF (lnSuccess <> 1) THEN
    ? loJwe2.LastErrorText
    RELEASE loJpgBytes
    RELEASE loJwe
    RELEASE loJweProtHdr
    RELEASE loSbJwe
    RELEASE loJwe2
    RELEASE loJpgOriginal
    CANCEL
ENDIF

? "Decrypted JPG size = " + STR(loJpgOriginal.NumBytes)

* Save the decrypted JPG to a file.
lnSuccess = loJpgOriginal.WriteFile("qa_output/jwe_decrypted_starfish.jpg")

? "success = " + STR(lnSuccess)

* The output of this program, when tested, was:
* Original JPG size = 6229
* eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.9YFz_wteV ... 7Et3hKhpxnKEXw
* size of JWE: 8473
* Decrypted JPG size = 6229
* success = True

RELEASE loJpgBytes
RELEASE loJwe
RELEASE loJweProtHdr
RELEASE loSbJwe
RELEASE loJwe2
RELEASE loJpgOriginal