(C#) JWE Using Flattened JWE JSON Serialization

This example duplicates the example A.5 in RFC 7516 for JSON Web Encryption (JWE).

This example demonstrates using the flattened JWE JSON Serialization syntax. This example demonstrates the capability for encrypting the plaintext to a single recipient in a flattened JSON structure.

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.

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

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

// First build the JWE Protected Header: {"enc":"A128CBC-HS256"}
Chilkat.JsonObject jweProtHdr = new Chilkat.JsonObject();
jweProtHdr.AppendString("enc","A128CBC-HS256");
jwe.SetProtectedHeader(jweProtHdr);

// We have a single recipient that uses AES Key Wrap to encrypt the CEK.
// 
//      {"alg":"A128KW","kid":"7"}

Chilkat.JsonObject jweRecipientHdr = new Chilkat.JsonObject();
jweRecipientHdr.AppendString("alg","A128KW");
jweRecipientHdr.AppendString("kid","7");
int recipientIndex = 0;
jwe.SetRecipientHeader(recipientIndex,jweRecipientHdr);

// Set the Shared Unprotected Header:  {"jku":"https://server.example.com/keys.jwks"}
Chilkat.JsonObject jweUnprotHdr = new Chilkat.JsonObject();
jweUnprotHdr.AppendString("jku","https://server.example.com/keys.jwks");
jwe.SetUnprotectedHeader(jweUnprotHdr);

// Set the AES key wrapping key.
string aesWrappingKey = "GawgguFyGrWKav7AX4VKUg";
recipientIndex = 0;
jwe.SetWrappingKey(recipientIndex,aesWrappingKey,"base64url");

// OK.. everything has been specified.
// Now encrypt.  
// Indicate that we prefer the flattened JSON serialization.
jwe.PreferFlattened = true;
string strJwe = jwe.Encrypt(plaintext,"utf-8");
if (jwe.LastMethodSuccess != true) {
    Debug.WriteLine(jwe.LastErrorText);
    return;
}

// The JWE is produced in the most compact form possible (a single line).
// Let's load it into a JSON object and examine in a non-compact pretty-printed format:
Chilkat.JsonObject jsonTemp = new Chilkat.JsonObject();
jsonTemp.Load(strJwe);
jsonTemp.EmitCompact = false;
Debug.WriteLine(jsonTemp.Emit());

// The JWE looks like this:
// (Note: Because of random values used in the encryption process, your encrypted results will be different.)

// 	{ 
// 	  "protected": "eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
// 	  "unprotected": { 
// 	    "jku": "https://server.example.com/keys.jwks"
// 	  },
// 	  "header": { 
// 	    "alg": "A128KW",
// 	    "kid": "7"
// 	  },
// 	  "encrypted_key": "FW7z9VxOvnF2ClicvUT4HTeqcdyh90C6qytfEFJsOb77FOwTfYrc3w",
// 	  "iv": "O6Ly5-eML3zTs-_fNX3D5Q",
// 	  "ciphertext": "Q8NLmeac9JhLh0CQPuG_7D9wVDb55eToCh0g5-FQ4M0",
// 	  "tag": "slzlo6-J9C7wSDF4dh_kBg"
// 	} 

// Now decrypt......................................

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

// Set the AES wrap key..
recipientIndex = 0;
jwe2.SetWrappingKey(recipientIndex,aesWrappingKey,"base64url");

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

Debug.WriteLine("original text decrypted with AES key wrap key: ");
Debug.WriteLine(originalPlaintext);

// ---------------------------------------------------------------------------------
// It should also be possible to decrypt the flattened JWE as shown in RFC 7516, Appendix A.5
// because it was produced using the same key.

Chilkat.StringBuilder sbJwe = new Chilkat.StringBuilder();

sbJwe.Append("{");
sbJwe.Append("\"protected\":");
sbJwe.Append("\"eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0\",");
sbJwe.Append("\"unprotected\":");
sbJwe.Append("{\"jku\":\"https://server.example.com/keys.jwks\"},");
sbJwe.Append("\"header\":");
sbJwe.Append("{\"alg\":\"A128KW\",\"kid\":\"7\"},");
sbJwe.Append("\"encrypted_key\":");
sbJwe.Append("\"6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ\",");
sbJwe.Append("\"iv\":");
sbJwe.Append("\"AxY8DCtDaGlsbGljb3RoZQ\",");
sbJwe.Append("\"ciphertext\":");
sbJwe.Append("\"KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY\",");
sbJwe.Append("\"tag\":");
sbJwe.Append("\"Mz-VPPyU4RlcuYv1IwIvzw\"");
sbJwe.Append("}");

success = jwe2.LoadJweSb(sbJwe);
if (success != true) {
    Debug.WriteLine(jwe2.LastErrorText);
    return;
}

recipientIndex = 0;
jwe2.SetWrappingKey(recipientIndex,aesWrappingKey,"base64url");

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

Debug.WriteLine("original text decrypted from published flattened JWE: ");
Debug.WriteLine(originalPlaintext);

// The output:

// original text decrypted with AES key wrap key: 
// Live long and prosper.
// original text decrypted from published flattened JWE: 
// Live long and prosper.