(Lianja) 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.

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// 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."

loJwe = createobject("CkJwe")

// First build the JWE Protected Header..
loJweProtHdr = createobject("CkJsonObject")
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.
loPrng = createobject("CkPrng")
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 <> .T.) then
    ? loJwe.LastErrorText
    release loJwe
    release loJweProtHdr
    release loPrng
    return
endif

// Show the JWE we just created:
? lcStrJwe

// Decrypt the JWE.
loJwe2 = createobject("CkJwe")
llSuccess = loJwe2.LoadJwe(lcStrJwe)
if (llSuccess <> .T.) then
    ? loJwe2.LastErrorText
    release loJwe
    release loJweProtHdr
    release loPrng
    release loJwe2
    return
endif

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

// Decrypt.
lcOriginalPlaintext = loJwe2.Decrypt(0,"utf-8")
if (loJwe2.LastMethodSuccess <> .T.) then
    ? loJwe2.LastErrorText
    release loJwe
    release loJweProtHdr
    release loPrng
    release loJwe2
    return
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