(C# UWP/WinRT) 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 Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

// 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.

bool success;
string plaintext = "Live long and prosper.";

Chilkat.Jwe jwe = new Chilkat.Jwe();

// First build the JWE Protected Header..
Chilkat.JsonObject jweProtHdr = new Chilkat.JsonObject();
jweProtHdr.AppendString("alg","PBES2-HS256+A128KW");
jweProtHdr.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.
Chilkat.Prng prng = new Chilkat.Prng();
jweProtHdr.AppendString("p2s",prng.GenRandom(16,"base64url"));
jweProtHdr.AppendString("p2c","1000");

Debug.WriteLine("JWE Protected Header: " + jweProtHdr.Emit());
Debug.WriteLine("--");

// Don't forget to actually provide the protected header to the JWE object:
jwe.SetProtectedHeader(jweProtHdr);

// Set the PBES2 password
int recipientIndex = 0;
jwe.SetPassword(recipientIndex,"top secret");

// Encrypt and return the JWE:
string strJwe = jwe.Encrypt(plaintext,"utf-8");
if (jwe.LastMethodSuccess != true) {
    Debug.WriteLine(jwe.LastErrorText);
    return;
}

// Show the JWE we just created:
Debug.WriteLine(strJwe);

// Decrypt the JWE.
Chilkat.Jwe jwe2 = new Chilkat.Jwe();
success = jwe2.LoadJwe(strJwe);
if (success != true) {
    Debug.WriteLine(jwe2.LastErrorText);
    return;
}

// Set the PBES2 password
jwe2.SetPassword(recipientIndex,"top secret");

// Decrypt.
string originalPlaintext = jwe2.Decrypt(0,"utf-8");
if (jwe2.LastMethodSuccess != true) {
    Debug.WriteLine(jwe2.LastErrorText);
    return;
}

Debug.WriteLine("original text: ");
Debug.WriteLine(originalPlaintext);

// 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.