(Visual FoxPro) JWE using PBES2 Key Wrapping

Demonstrates how to create and decrypt a JWE that using PBES2 key wrapping.

This example demonstrates PBES2 with HMAC SHA-256 and A128KW wrapping. It is also possible to do the following by simply changing the "alg" parameter:

• PBES2 with HMAC SHA-384 and A192KW wrapping
• PBES2 with HMAC SHA-512 and A256KW wrapping

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 lcPlaintext
LOCAL loJwe
LOCAL loJweProtHdr
LOCAL loPrng
LOCAL lnRecipientIndex
LOCAL lcStrJwe
LOCAL loJwe2
LOCAL lcOriginalPlaintext

* 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.

lcPlaintext = "Live long and prosper."

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

* First build the JWE Protected Header..
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJweProtHdr = CreateObject('Chilkat.JsonObject')
loJweProtHdr.AppendString("alg","PBES2-HS256+A128KW")
loJweProtHdr.AppendString("enc","A128GCM")

* PBES2 requires two additional parameters:
* 1) A random salt parameter ("p2s") containing 8 or more bytes in base64url format.
* 2) An iteration count parameter ("p2c").  A minimum count of 1000 is recommended.
*    The iteration count is intended to make the PBES2 computation more expensive (time consuming)
*    to prevent brute-force attacks.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Prng')
loPrng = CreateObject('Chilkat.Prng')
loJweProtHdr.AppendString("p2s",loPrng.GenRandom(16,"base64url"))
loJweProtHdr.AppendString("p2c","1000")

? "JWE Protected Header: " + loJweProtHdr.Emit()
? "--"

* Don't forget to actually provide the protected header to the JWE object:
loJwe.SetProtectedHeader(loJweProtHdr)

* Set the PBES2 password
lnRecipientIndex = 0
loJwe.SetPassword(lnRecipientIndex,"top secret")

* Encrypt and return the JWE:
lcStrJwe = loJwe.Encrypt(lcPlaintext,"utf-8")
IF (loJwe.LastMethodSuccess <> 1) THEN
    ? loJwe.LastErrorText
    RELEASE loJwe
    RELEASE loJweProtHdr
    RELEASE loPrng
    CANCEL
ENDIF

* Show the JWE we just created:
? lcStrJwe

* Decrypt the JWE.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Jwe')
loJwe2 = CreateObject('Chilkat.Jwe')
lnSuccess = loJwe2.LoadJwe(lcStrJwe)
IF (lnSuccess <> 1) THEN
    ? loJwe2.LastErrorText
    RELEASE loJwe
    RELEASE loJweProtHdr
    RELEASE loPrng
    RELEASE loJwe2
    CANCEL
ENDIF

* Set the PBES2 password
loJwe2.SetPassword(lnRecipientIndex,"top secret")

* Decrypt.
lcOriginalPlaintext = loJwe2.Decrypt(0,"utf-8")
IF (loJwe2.LastMethodSuccess <> 1) THEN
    ? loJwe2.LastErrorText
    RELEASE loJwe
    RELEASE loJweProtHdr
    RELEASE loPrng
    RELEASE loJwe2
    CANCEL
ENDIF

? "original text: "
? lcOriginalPlaintext

* Sample output:

* JWE Protected Header: {"alg":"PBES2-HS256+A128KW","enc":"A128GCM","p2s":"z39rTEfRy1T1Yn_D1mZRlg","p2c":"1000"}
* --
* eyJhbGciOiJQQkVTMi1IUzI1NitBMTI4S1ciLCJlbmMiOiJBMTI4R0NNIiwicDJzIjoiejM5clRFZlJ5MVQxWW5fRDFtWlJsZyIsInAyYyI6IjEwMDAifQ.koYt6PrFmYwcwdcT7ZcvXHA1d-Xez5h4.luGlbvEnZp-7IsBOj42Yhw.YMTcfLf8Qe4zazozGV2OAu3cUdQ8Kg.rWub47ESWkc6IqZJTvSTmg
* original text: 
* Live long and prosper.

RELEASE loJwe
RELEASE loJweProtHdr
RELEASE loPrng
RELEASE loJwe2