(Delphi DLL) 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.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Jwe, StringBuilder, PrivateKey, PublicKey, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
plaintext: PWideChar;
jweProtHdr: HCkJsonObject;
sbJwk: HCkStringBuilder;
rsaPrivKey: HCkPrivateKey;
rsaPubKey: HCkPublicKey;
jwe: HCkJwe;
strJwe: PWideChar;
jwe2: HCkJwe;
originalPlaintext: PWideChar;
sbJwe: HCkStringBuilder;

begin
// 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.

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"}
jweProtHdr := CkJsonObject_Create();
CkJsonObject_AppendString(jweProtHdr,'alg','RSA-OAEP');
CkJsonObject_AppendString(jweProtHdr,'enc','A256GCM');
Memo1.Lines.Add('JWE Protected Header: ' + CkJsonObject__emit(jweProtHdr));
Memo1.Lines.Add('--');

// ---------------------------------
// 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:
sbJwk := CkStringBuilder_Create();
CkStringBuilder_Append(sbJwk,'{"kty": "RSA",');
CkStringBuilder_Append(sbJwk,'"n": "oahUIoWw0K0usKNuOR6H4wkf4oBUXHTxRvgb48E-BVvxkeDNjbC4he8rUW');
CkStringBuilder_Append(sbJwk,'cJoZmds2h7M70imEVhRU5djINXtqllXI4DFqcI1DgjT9LewND8MW2Krf3S');
CkStringBuilder_Append(sbJwk,'psk_ZkoFnilakGygTwpZ3uesH-PFABNIUYpOiN15dsQRkgr0vEhxN92i2a');
CkStringBuilder_Append(sbJwk,'sbOenSZeyaxziK72UwxrrKoExv6kc5twXTq4h-QChLOln0_mtUZwfsRaMS');
CkStringBuilder_Append(sbJwk,'tPs6mS6XrgxnxbWhojf663tuEQueGC-FCMfra36C9knDFGzKsNa7LZK2dj');
CkStringBuilder_Append(sbJwk,'YgyD3JR_MB_4NUJW_TqOQtwHYbxevoJArm-L5StowjzGy-_bq6Gw",');
CkStringBuilder_Append(sbJwk,'"e": "AQAB",');
CkStringBuilder_Append(sbJwk,'"d": "kLdtIj6GbDks_ApCSTYQtelcNttlKiOyPzMrXHeI-yk1F7-kpDxY4-WY5N');
CkStringBuilder_Append(sbJwk,'WV5KntaEeXS1j82E375xxhWMHXyvjYecPT9fpwR_M9gV8n9Hrh2anTpTD9');
CkStringBuilder_Append(sbJwk,'3Dt62ypW3yDsJzBnTnrYu1iwWRgBKrEYY46qAZIrA2xAwnm2X7uGR1hghk');
CkStringBuilder_Append(sbJwk,'qDp0Vqj3kbSCz1XyfCs6_LehBwtxHIyh8Ripy40p24moOAbgxVw3rxT_vl');
CkStringBuilder_Append(sbJwk,'t3UVe4WO3JkJOzlpUf-KTVI2Ptgm-dARxTEtE-id-4OJr0h-K-VFs3VSnd');
CkStringBuilder_Append(sbJwk,'VTIznSxfyrj8ILL6MG_Uv8YAu7VILSB3lOW085-4qE3DzgrTjgyQ",');
CkStringBuilder_Append(sbJwk,'"p": "1r52Xk46c-LsfB5P442p7atdPUrxQSy4mti_tZI3Mgf2EuFVbUoDBvaRQ-');
CkStringBuilder_Append(sbJwk,'SWxkbkmoEzL7JXroSBjSrK3YIQgYdMgyAEPTPjXv_hI2_1eTSPVZfzL0lf');
CkStringBuilder_Append(sbJwk,'fNn03IXqWF5MDFuoUYE0hzb2vhrlN_rKrbfDIwUbTrjjgieRbwC6Cl0",');
CkStringBuilder_Append(sbJwk,'"q": "wLb35x7hmQWZsWJmB_vle87ihgZ19S8lBEROLIsZG4ayZVe9Hi9gDVCOBm');
CkStringBuilder_Append(sbJwk,'UDdaDYVTSNx_8Fyw1YYa9XGrGnDew00J28cRUoeBB_jKI1oma0Orv1T9aX');
CkStringBuilder_Append(sbJwk,'IWxKwd4gvxFImOWr3QRL9KEBRzk2RatUBnmDZJTIAfwTs0g68UZHvtc",');
CkStringBuilder_Append(sbJwk,'"dp": "ZK-YwE7diUh0qR1tR7w8WHtolDx3MZ_OTowiFvgfeQ3SiresXjm9gZ5KL');
CkStringBuilder_Append(sbJwk,'hMXvo-uz-KUJWDxS5pFQ_M0evdo1dKiRTjVw_x4NyqyXPM5nULPkcpU827');
CkStringBuilder_Append(sbJwk,'rnpZzAJKpdhWAgqrXGKAECQH0Xt4taznjnd_zVpAmZZq60WPMBMfKcuE",');
CkStringBuilder_Append(sbJwk,'"dq": "Dq0gfgJ1DdFGXiLvQEZnuKEN0UUmsJBxkjydc3j4ZYdBiMRAy86x0vHCj');
CkStringBuilder_Append(sbJwk,'ywcMlYYg4yoC4YZa9hNVcsjqA3FeiL19rk8g6Qn29Tt0cj8qqyFpz9vNDB');
CkStringBuilder_Append(sbJwk,'UfCAiJVeESOjJDZPYHdHY8v1b-o-Z2X5tvLx-TCekf7oxyeKDUqKWjis",');
CkStringBuilder_Append(sbJwk,'"qi": "VIMpMYbPf47dT1w_zDUXfPimsSegnMOA1zTaX7aGk_8urY6R8-ZW1FxU7');
CkStringBuilder_Append(sbJwk,'AlWAyLWybqq6t16VFd7hQd0y6flUK4SlOydB61gwanOsXGOAOv82cHq0E3');
CkStringBuilder_Append(sbJwk,'eL4HrtZkUuKvnPrMnsUUFlfUdybVzxyjz9JF_XyaY14ardLSjf4L_FNY"}');

// Load this JWK into a Chilkat private key object.
rsaPrivKey := CkPrivateKey_Create();
success := CkPrivateKey_LoadJwk(rsaPrivKey,CkStringBuilder__getAsString(sbJwk));
if (success <> True) then
  begin
    Memo1.Lines.Add(CkPrivateKey__lastErrorText(rsaPrivKey));
    Exit;
  end;

// 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
rsaPubKey := CkPrivateKey_GetPublicKey(rsaPrivKey);

// ---------------------------------
// 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).

jwe := CkJwe_Create();
CkJwe_SetProtectedHeader(jwe,jweProtHdr);
CkJwe_SetPublicKey(jwe,0,rsaPubKey);
CkPublicKey_Dispose(rsaPubKey);

strJwe := CkJwe__encrypt(jwe,plaintext,'utf-8');
if (CkJwe_getLastMethodSuccess(jwe) <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe));
    Exit;
  end;

// 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.)
Memo1.Lines.Add(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.
jwe2 := CkJwe_Create();
success := CkJwe_LoadJwe(jwe2,strJwe);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe2));
    Exit;
  end;

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

// Decrypt.
originalPlaintext := CkJwe__decrypt(jwe2,0,'utf-8');
if (CkJwe_getLastMethodSuccess(jwe2) <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe2));
    Exit;
  end;

Memo1.Lines.Add('original text: ');
Memo1.Lines.Add(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.

sbJwe := CkStringBuilder_Create();
CkStringBuilder_Append(sbJwe,'eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.');
CkStringBuilder_Append(sbJwe,'OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe');
CkStringBuilder_Append(sbJwe,'ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb');
CkStringBuilder_Append(sbJwe,'Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV');
CkStringBuilder_Append(sbJwe,'mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8');
CkStringBuilder_Append(sbJwe,'1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi');
CkStringBuilder_Append(sbJwe,'6UklfCpIMfIjf7iGdXKHzg.');
CkStringBuilder_Append(sbJwe,'48V1_ALb6US04U3b.');
CkStringBuilder_Append(sbJwe,'5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji');
CkStringBuilder_Append(sbJwe,'SdiwkIr3ajwQzaBtQD_A.');
CkStringBuilder_Append(sbJwe,'XFBoMYUZodetZdvTiFvSkQ');

success := CkJwe_LoadJweSb(jwe2,sbJwe);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe2));
    Exit;
  end;

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

// Decrypt.
originalPlaintext := CkJwe__decrypt(jwe2,0,'utf-8');
if (CkJwe_getLastMethodSuccess(jwe2) <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe2));
    Exit;
  end;

Memo1.Lines.Add(originalPlaintext);

CkJsonObject_Dispose(jweProtHdr);
CkStringBuilder_Dispose(sbJwk);
CkPrivateKey_Dispose(rsaPrivKey);
CkJwe_Dispose(jwe);
CkJwe_Dispose(jwe2);
CkStringBuilder_Dispose(sbJwe);

end;