(Android™) JWE Using General JWE JSON Serialization

This example duplicates the example A.4 in RFC 7516 for JSON Web Encryption (JWE).

This example demonstrates the capability for encrypting the same plaintext to multiple recipients. Two recipients are present in this example.

Note: This example requires Chilkat v9.5.0.66 or greater.

Chilkat Android™ Downloads Android™ Java Libraries Android C/C++ Libraries

// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // 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.

    boolean success;
    String plaintext = "Live long and prosper.";

    CkJwe jwe = new CkJwe();

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

    // The first recipient uses the RSAES-PKCS1-v1_5 algorithm to encrypt
    // the CEK.  The second uses AES Key Wrap to encrypt the CEK.  Key ID
    // values are supplied for both keys.  The two JWE Per-Recipient
    // Unprotected Header values used to represent these algorithms and key
    // IDs are:
    // 
    //      {"alg":"RSA1_5","kid":"2011-04-29"}
    // 
    // and
    // 
    //      {"alg":"A128KW","kid":"7"}

    CkJsonObject jweRecipientHdr1 = new CkJsonObject();
    jweRecipientHdr1.AppendString("alg","RSA1_5");
    jweRecipientHdr1.AppendString("kid","2011-04-29");
    int recipientIndex = 0;
    jwe.SetRecipientHeader(recipientIndex,jweRecipientHdr1);

    CkJsonObject jweRecipientHdr2 = new CkJsonObject();
    jweRecipientHdr2.AppendString("alg","A128KW");
    jweRecipientHdr2.AppendString("kid","7");
    recipientIndex = 1;
    jwe.SetRecipientHeader(recipientIndex,jweRecipientHdr2);

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

    // Note: The intent of specifying a "kid" (an acronym for "Key ID") is that
    // the software would somehow download the keys.jwks from https://server.example.com/keys.jwks,
    // and would select the key (whatever format it may be, such as RSA, or an AES key wrap key, etc.),
    // and then automatically use it. 

    // This example keeps the "kid" and "jku" in their respective headers, but does not actually fetch
    // the keys from some URL.  We'll just provide the keys directly..

    // Recipient 0 uses this RSA key:
    CkStringBuilder sbJwk = new CkStringBuilder();
    sbJwk.Append("{\"kty\":\"RSA\",");
    sbJwk.Append("\"n\":\"sXchDaQebHnPiGvyDOAT4saGEUetSyo9MKLOoWFsueri23bOdgWp4Dy1Wl");
    sbJwk.Append("UzewbgBHod5pcM9H95GQRV3JDXboIRROSBigeC5yjU1hGzHHyXss8UDpre");
    sbJwk.Append("cbAYxknTcQkhslANGRUZmdTOQ5qTRsLAt6BTYuyvVRdhS8exSZEy_c4gs_");
    sbJwk.Append("7svlJJQ4H9_NxsiIoLwAEk7-Q3UXERGYw_75IDrGA84-lA_-Ct4eTlXHBI");
    sbJwk.Append("Y2EaV7t7LjJaynVJCpkv4LKjTTAumiGUIuQhrNhZLuF_RJLqHpM2kgWFLU");
    sbJwk.Append("7-VTdL1VbC2tejvcI2BlMkEpk1BzBZI0KQB0GaDWFLN-aEAw3vRw\",");
    sbJwk.Append("\"e\":\"AQAB\",");
    sbJwk.Append("\"d\":\"VFCWOqXr8nvZNyaaJLXdnNPXZKRaWCjkU5Q2egQQpTBMwhprMzWzpR8Sxq");
    sbJwk.Append("1OPThh_J6MUD8Z35wky9b8eEO0pwNS8xlh1lOFRRBoNqDIKVOku0aZb-ry");
    sbJwk.Append("nq8cxjDTLZQ6Fz7jSjR1Klop-YKaUHc9GsEofQqYruPhzSA-QgajZGPbE_");
    sbJwk.Append("0ZaVDJHfyd7UUBUKunFMScbflYAAOYJqVIVwaYR5zWEEceUjNnTNo_CVSj");
    sbJwk.Append("-VvXLO5VZfCUAVLgW4dpf1SrtZjSt34YLsRarSb127reG_DUwg9Ch-Kyvj");
    sbJwk.Append("T1SkHgUWRVGcyly7uvVGRSDwsXypdrNinPA4jlhoNdizK2zF2CWQ\",");
    sbJwk.Append("\"p\":\"9gY2w6I6S6L0juEKsbeDAwpd9WMfgqFoeA9vEyEUuk4kLwBKcoe1x4HG68");
    sbJwk.Append("ik918hdDSE9vDQSccA3xXHOAFOPJ8R9EeIAbTi1VwBYnbTp87X-xcPWlEP");
    sbJwk.Append("krdoUKW60tgs1aNd_Nnc9LEVVPMS390zbFxt8TN_biaBgelNgbC95sM\",");
    sbJwk.Append("\"q\":\"uKlCKvKv_ZJMVcdIs5vVSU_6cPtYI1ljWytExV_skstvRSNi9r66jdd9-y");
    sbJwk.Append("BhVfuG4shsp2j7rGnIio901RBeHo6TPKWVVykPu1iYhQXw1jIABfw-MVsN");
    sbJwk.Append("-3bQ76WLdt2SDxsHs7q7zPyUyHXmps7ycZ5c72wGkUwNOjYelmkiNS0\",");
    sbJwk.Append("\"dp\":\"w0kZbV63cVRvVX6yk3C8cMxo2qCM4Y8nsq1lmMSYhG4EcL6FWbX5h9yuv");
    sbJwk.Append("ngs4iLEFk6eALoUS4vIWEwcL4txw9LsWH_zKI-hwoReoP77cOdSL4AVcra");
    sbJwk.Append("Hawlkpyd2TWjE5evgbhWtOxnZee3cXJBkAi64Ik6jZxbvk-RR3pEhnCs\",");
    sbJwk.Append("\"dq\":\"o_8V14SezckO6CNLKs_btPdFiO9_kC1DsuUTd2LAfIIVeMZ7jn1Gus_Ff");
    sbJwk.Append("7B7IVx3p5KuBGOVF8L-qifLb6nQnLysgHDh132NDioZkhH7mI7hPG-PYE_");
    sbJwk.Append("odApKdnqECHWw0J-F0JWnUd6D2B_1TvF9mXA2Qx-iGYn8OVV1Bsmp6qU\",");
    sbJwk.Append("\"qi\":\"eNho5yRBEBxhGBtQRww9QirZsB66TrfFReG_CcteI1aCneT0ELGhYlRlC");
    sbJwk.Append("tUkTRclIfuEPmNsNDPbLoLqqCVznFbvdB7x-Tl-m0l_eFTj2KiqwGqE9PZ");
    sbJwk.Append("B9nNTwMVvH3VRRSLWACvPnSiwP8N5Usy-WRXS-V7TbpxIhvepTfE0NNo\"");
    sbJwk.Append("}");

    // Load this JWK into a Chilkat private key object.
    CkPrivateKey rsaPrivKey = new CkPrivateKey();
    success = rsaPrivKey.LoadJwk(sbJwk.getAsString());
    if (success != true) {
        Log.i(TAG, rsaPrivKey.lastErrorText());
        return;
        }

    // Get the public key for encryption.  (The RSA private key is used for decryption.)
    CkPublicKey rsaPubKey = rsaPrivKey.GetPublicKey();
    recipientIndex = 0;
    jwe.SetPublicKey(recipientIndex,rsaPubKey);

    // Recipient 1 uses AES Key Wrap
    String aesWrappingKey = "GawgguFyGrWKav7AX4VKUg";
    recipientIndex = 1;
    jwe.SetWrappingKey(recipientIndex,aesWrappingKey,"base64url");

    // OK.. everything has been specified.
    // Now encrypt.  Chilkat will use the general JSON serialization because it is only
    // possible serializationto use given there are multiple recipients. 
    String strJwe = jwe.encrypt(plaintext,"utf-8");
    if (jwe.get_LastMethodSuccess() != true) {
        Log.i(TAG, jwe.lastErrorText());
        return;
        }

    // The strJwe is 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:
    CkJsonObject jsonTemp = new CkJsonObject();
    jsonTemp.Load(strJwe);
    jsonTemp.put_EmitCompact(false);
    Log.i(TAG, 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"
    // 	  },
    // 	  "recipients": [
    // 	    { 
    // 	      "header": { 
    // 	        "alg": "RSA1_5",
    // 	        "kid": "2011-04-29"
    // 	      },
    // 	      "encrypted_key": "WlUggejR-vStJVNKgjG2mQrVv74aga1FFutT8E-n-yJEOTsOVnGjhj1NW_Snd9DqHAhFrc7NEvKCFplKWGnusBZxxjm1JpdUa0MIpkGmncJHQQdfm21vcbEUbDmfqVY79SnEis3tih1D3qmyp_Bxti4byDAHJIOJv_cj0Sx8oHZzgGtOLjtHsydyo1MtBIqI0w86i_uhUuraihZ3ngj67YZ6uqpR6lulkPIVohfF3oJ0D3Ay_XOCHWlHYkTg6VZsa0FDrPtfB2pG3TxTBPwI4IMj5uF_D3zrg51dCYKU1Gah71ujLaXRE5q9XF7oOknxiWQuWc7Ox8JP03lSx-DiVA"
    // 	    },
    // 	    { 
    // 	      "header": { 
    // 	        "alg": "A128KW",
    // 	        "kid": "7"
    // 	      },
    // 	      "encrypted_key": "8diBP2aUUB_Jl5WxCuMJLN6HsppE3rhSjcecee0fBcwB31zbPAVejQ"
    // 	    } 
    // 	  ],
    // 	  "iv": "JqahFKx5Z8SFT_LnkfOq0Q",
    // 	  "ciphertext": "YcSdjlszsaY1ADcs4Vw85H_WoAqnkDIJaJsTkmCj05s",
    // 	  "tag": "G3KF2CZ-DMhm0cqUbhJKMA"
    // 	} 

    // To decrypt, we don't need both recipient keys.  We can decrypt with one key or the other.
    // The FindRecipient method can be used to find a particular recipient index.

    // First, load the JWE..
    CkJwe jwe2 = new CkJwe();
    success = jwe2.LoadJwe(strJwe);
    if (success != true) {
        Log.i(TAG, jwe2.lastErrorText());
        return;
        }

    // Let's say we have the AES key wrap key, and we know the "kid" equals "7".
    boolean caseSensitive = false;
    recipientIndex = jwe2.FindRecipient("kid","7",caseSensitive);
    if (recipientIndex < 0) {
        Log.i(TAG, "Unable to find recipient with kid=7");
        return;
        }

    // Set the AES wrap key for the recipient index.
    jwe2.SetWrappingKey(recipientIndex,aesWrappingKey,"base64url");

    // Decrypt
    String originalPlaintext = jwe2.decrypt(recipientIndex,"utf-8");
    if (jwe2.get_LastMethodSuccess() != true) {
        Log.i(TAG, jwe2.lastErrorText());
        return;
        }

    Log.i(TAG, "original text decrypted with AES key wrap key: ");
    Log.i(TAG, originalPlaintext);

    // Now, let's do the same with the RSA private key:
    recipientIndex = jwe2.FindRecipient("kid","2011-04-29",caseSensitive);
    if (recipientIndex < 0) {
        Log.i(TAG, "Unable to find recipient with kid=2011-04-29");
        return;
        }

    // Set the RSA private key for the recipient index.
    jwe2.SetPrivateKey(recipientIndex,rsaPrivKey);

    // Decrypt
    originalPlaintext = jwe2.decrypt(recipientIndex,"utf-8");
    if (jwe2.get_LastMethodSuccess() != true) {
        Log.i(TAG, jwe2.lastErrorText());
        return;
        }

    Log.i(TAG, "original text decrypted with RSA private key: ");
    Log.i(TAG, originalPlaintext);

    // ---------------------------------------------------------------------------------
    // It should also be possible to decrypt the JWE as shown in RFC 7516, Appendix A.4.7
    // because it was produced using the same keys.

    CkStringBuilder sbJwe = new CkStringBuilder();
    sbJwe.Append("{");
    sbJwe.Append("\"protected\":");
    sbJwe.Append("\"eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0\",");
    sbJwe.Append("\"unprotected\":");
    sbJwe.Append("{\"jku\":\"https://server.example.com/keys.jwks\"},");
    sbJwe.Append("\"recipients\":[");
    sbJwe.Append("{\"header\":");
    sbJwe.Append("{\"alg\":\"RSA1_5\",\"kid\":\"2011-04-29\"},");
    sbJwe.Append("\"encrypted_key\":");
    sbJwe.Append("\"UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-");
    sbJwe.Append("kFm1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKx");
    sbJwe.Append("GHZ7PcHALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3");
    sbJwe.Append("YvkkysZIFNPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPh");
    sbJwe.Append("cCdZ6XDP0_F8rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPg");
    sbJwe.Append("wCp6X-nZZd9OHBv-B3oWh2TbqmScqXMR4gp_A\"},");
    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) {
        Log.i(TAG, jwe2.lastErrorText());
        return;
        }

    // We can decrypt with either key.  Let's use the AES key wrap key...
    recipientIndex = jwe2.FindRecipient("kid","7",caseSensitive);
    if (recipientIndex < 0) {
        Log.i(TAG, "Unable to find recipient with kid=7");
        return;
        }

    // Set the AES wrap key for the recipient index.
    jwe2.SetWrappingKey(recipientIndex,aesWrappingKey,"base64url");

    // Decrypt
    originalPlaintext = jwe2.decrypt(recipientIndex,"utf-8");
    if (jwe2.get_LastMethodSuccess() != true) {
        Log.i(TAG, jwe2.lastErrorText());
        return;
        }

    Log.i(TAG, "original text decrypted from published JWE, with AES key wrap key: ");
    Log.i(TAG, originalPlaintext);

    // The output:

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

  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}