(C#) JWE using RSAES-OAEP and AES GCM

This example duplicates the example A.1 in RFC 7516 for JSON Web Encryption (JWE).

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 = "The true sign of intelligence is not knowledge but imagination.";

// ---------------------------------
// A.1.1 JOSE Header
// First build the JWE Protected Header.
// We want to build this: {"alg":"RSA-OAEP","enc":"A256GCM"}
Chilkat.JsonObject jweProtHdr = new Chilkat.JsonObject();
jweProtHdr.AppendString("alg","RSA-OAEP");
jweProtHdr.AppendString("enc","A256GCM");
Debug.WriteLine("JWE Protected Header: " + jweProtHdr.Emit());
Debug.WriteLine("--");

// ---------------------------------
// A.1.2 Content Encryption Key
// Note: Chilkat automatically generates the random CEK internally.
// The application does not need to explicitly take this step.

// ---------------------------------
// A.1.3.  Key Encryption
// The application should load an RSA private key from any format.
// However, the application does not need to explicitly construct the JWE Encrypted Key.
// Chilkat automatically does it internally.
// The design of the Chilkat JWE API is to allow the application to create the JWE
// after specifying the inputs.  (This is in contrast to forcing the application developer
// to painstakingly go through each step of the JWE construction process.)

// The specific RSA key used in the A.1 example is the following JWK:
Chilkat.StringBuilder sbJwk = new Chilkat.StringBuilder();
sbJwk.Append("{\"kty\": \"RSA\",");
sbJwk.Append("\"n\": \"oahUIoWw0K0usKNuOR6H4wkf4oBUXHTxRvgb48E-BVvxkeDNjbC4he8rUW");
sbJwk.Append("cJoZmds2h7M70imEVhRU5djINXtqllXI4DFqcI1DgjT9LewND8MW2Krf3S");
sbJwk.Append("psk_ZkoFnilakGygTwpZ3uesH-PFABNIUYpOiN15dsQRkgr0vEhxN92i2a");
sbJwk.Append("sbOenSZeyaxziK72UwxrrKoExv6kc5twXTq4h-QChLOln0_mtUZwfsRaMS");
sbJwk.Append("tPs6mS6XrgxnxbWhojf663tuEQueGC-FCMfra36C9knDFGzKsNa7LZK2dj");
sbJwk.Append("YgyD3JR_MB_4NUJW_TqOQtwHYbxevoJArm-L5StowjzGy-_bq6Gw\",");
sbJwk.Append("\"e\": \"AQAB\",");
sbJwk.Append("\"d\": \"kLdtIj6GbDks_ApCSTYQtelcNttlKiOyPzMrXHeI-yk1F7-kpDxY4-WY5N");
sbJwk.Append("WV5KntaEeXS1j82E375xxhWMHXyvjYecPT9fpwR_M9gV8n9Hrh2anTpTD9");
sbJwk.Append("3Dt62ypW3yDsJzBnTnrYu1iwWRgBKrEYY46qAZIrA2xAwnm2X7uGR1hghk");
sbJwk.Append("qDp0Vqj3kbSCz1XyfCs6_LehBwtxHIyh8Ripy40p24moOAbgxVw3rxT_vl");
sbJwk.Append("t3UVe4WO3JkJOzlpUf-KTVI2Ptgm-dARxTEtE-id-4OJr0h-K-VFs3VSnd");
sbJwk.Append("VTIznSxfyrj8ILL6MG_Uv8YAu7VILSB3lOW085-4qE3DzgrTjgyQ\",");
sbJwk.Append("\"p\": \"1r52Xk46c-LsfB5P442p7atdPUrxQSy4mti_tZI3Mgf2EuFVbUoDBvaRQ-");
sbJwk.Append("SWxkbkmoEzL7JXroSBjSrK3YIQgYdMgyAEPTPjXv_hI2_1eTSPVZfzL0lf");
sbJwk.Append("fNn03IXqWF5MDFuoUYE0hzb2vhrlN_rKrbfDIwUbTrjjgieRbwC6Cl0\",");
sbJwk.Append("\"q\": \"wLb35x7hmQWZsWJmB_vle87ihgZ19S8lBEROLIsZG4ayZVe9Hi9gDVCOBm");
sbJwk.Append("UDdaDYVTSNx_8Fyw1YYa9XGrGnDew00J28cRUoeBB_jKI1oma0Orv1T9aX");
sbJwk.Append("IWxKwd4gvxFImOWr3QRL9KEBRzk2RatUBnmDZJTIAfwTs0g68UZHvtc\",");
sbJwk.Append("\"dp\": \"ZK-YwE7diUh0qR1tR7w8WHtolDx3MZ_OTowiFvgfeQ3SiresXjm9gZ5KL");
sbJwk.Append("hMXvo-uz-KUJWDxS5pFQ_M0evdo1dKiRTjVw_x4NyqyXPM5nULPkcpU827");
sbJwk.Append("rnpZzAJKpdhWAgqrXGKAECQH0Xt4taznjnd_zVpAmZZq60WPMBMfKcuE\",");
sbJwk.Append("\"dq\": \"Dq0gfgJ1DdFGXiLvQEZnuKEN0UUmsJBxkjydc3j4ZYdBiMRAy86x0vHCj");
sbJwk.Append("ywcMlYYg4yoC4YZa9hNVcsjqA3FeiL19rk8g6Qn29Tt0cj8qqyFpz9vNDB");
sbJwk.Append("UfCAiJVeESOjJDZPYHdHY8v1b-o-Z2X5tvLx-TCekf7oxyeKDUqKWjis\",");
sbJwk.Append("\"qi\": \"VIMpMYbPf47dT1w_zDUXfPimsSegnMOA1zTaX7aGk_8urY6R8-ZW1FxU7");
sbJwk.Append("AlWAyLWybqq6t16VFd7hQd0y6flUK4SlOydB61gwanOsXGOAOv82cHq0E3");
sbJwk.Append("eL4HrtZkUuKvnPrMnsUUFlfUdybVzxyjz9JF_XyaY14ardLSjf4L_FNY\"}");

// Load this JWK into a Chilkat private key object.
Chilkat.PrivateKey rsaPrivKey = new Chilkat.PrivateKey();
success = rsaPrivKey.LoadJwk(sbJwk.GetAsString());
if (success != true) {
    Debug.WriteLine(rsaPrivKey.LastErrorText);
    return;
}

// The public key is used to encrypt (i.e. create the JWE), 
// and the private key is used to decrypt.
// The RSA public key is simply a subset of the private key.  The RSA public key
// is composed of the "n" and "e" members shown above.  These are also known as the
// modulus and exponent.
// We can simply get the public key object from the private key object
Chilkat.PublicKey rsaPubKey = rsaPrivKey.GetPublicKey();

// ---------------------------------
// A.1.4.  Initialization Vector
// Chilkat automatically generates the necessary random IV internally.  
// The application does not need to do this explicitly.

// ---------------------------------
// A.1.5.  Additional Authenticated Data
// The Additional Authenticated Data encryption parameter is
// ASCII(BASE64URL(UTF8(JWE Protected Header))).
// Again, Chilkat automatically takes care of this internally.
// The application does not need to explicitly take this step.

// ---------------------------------
// A.1.6.  Content Encryption
// Again... this step is handled by Chilkat internally.

// ---------------------------------
// A.1.7.  Complete Representation
// The application need only call the Encrypt, EncryptSb, or EncryptBd method
// return the fully assembled JWE.  
// The final representation in the Compact Serialization 
// is the string BASE64URL(UTF8(JWE Protected Header)) || '.' ||
// BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization
// Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE
// Authentication Tag).

Chilkat.Jwe jwe = new Chilkat.Jwe();
jwe.SetProtectedHeader(jweProtHdr);
jwe.SetPublicKey(0,rsaPubKey);

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

// Note: The RSA OAEP algorithm uses random padding bytes internally.
// Therefore, the results will appear different each time -- even if the
// identical plaintext is encrypted with the identical RSA key. 
// (Do not expect the appearance of the results to be the same as what
// is published in the RFC.  However, what is published in the RFC *should*
// be decryptable using the code that follows.)
Debug.WriteLine(strJwe);

// Let's decrypt the JWE that was just produced.
// Do the following to decrypt a JWE:
// 1) Load the JWE.
// 2) Set the private key for decryption.
// 3) Decrypt.
Chilkat.Jwe jwe2 = new Chilkat.Jwe();
success = jwe2.LoadJwe(strJwe);
if (success != true) {
    Debug.WriteLine(jwe2.LastErrorText);
    return;
}

// Provide the RSA private key for decryption.
// (The JWE was encrypted for a single recipient at index 0.)
jwe2.SetPrivateKey(0,rsaPrivKey);

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

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

// ---------------------------------------------------------------------------------
// It should also be possible to decrypt the JWE as shown in RFC 7516, Appendix A.1.7
// because it was produced using the same RSA key.

Chilkat.StringBuilder sbJwe = new Chilkat.StringBuilder();
sbJwe.Append("eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.");
sbJwe.Append("OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe");
sbJwe.Append("ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb");
sbJwe.Append("Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV");
sbJwe.Append("mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8");
sbJwe.Append("1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi");
sbJwe.Append("6UklfCpIMfIjf7iGdXKHzg.");
sbJwe.Append("48V1_ALb6US04U3b.");
sbJwe.Append("5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji");
sbJwe.Append("SdiwkIr3ajwQzaBtQD_A.");
sbJwe.Append("XFBoMYUZodetZdvTiFvSkQ");

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

// Provide the RSA private key for decryption.
jwe2.SetPrivateKey(0,rsaPrivKey);

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

Debug.WriteLine(originalPlaintext);