(Visual Basic 6.0) 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.

Dim success As Long
Dim plaintext As 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"}
Dim jweProtHdr As New ChilkatJsonObject
success = jweProtHdr.AppendString("alg","RSA-OAEP")
success = jweProtHdr.AppendString("enc","A256GCM")
Debug.Print "JWE Protected Header: " & jweProtHdr.Emit()
Debug.Print "--"

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

' Load this JWK into a Chilkat private key object.
Dim rsaPrivKey As New PrivateKey
success = rsaPrivKey.LoadJwk(sbJwk.GetAsString())
If (success <> 1) Then
    Debug.Print rsaPrivKey.LastErrorText
    Exit Sub
End If

' 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
Dim rsaPubKey As PublicKey
Set 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).

Dim jwe As New ChilkatJwe
success = jwe.SetProtectedHeader(jweProtHdr)
success = jwe.SetPublicKey(0,rsaPubKey)

Dim strJwe As String
strJwe = jwe.Encrypt(plaintext,"utf-8")
If (jwe.LastMethodSuccess <> 1) Then
    Debug.Print jwe.LastErrorText
    Exit Sub
End If

' 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.Print 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.
Dim jwe2 As New ChilkatJwe
success = jwe2.LoadJwe(strJwe)
If (success <> 1) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

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

' Decrypt.
Dim originalPlaintext As String
originalPlaintext = jwe2.Decrypt(0,"utf-8")
If (jwe2.LastMethodSuccess <> 1) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

Debug.Print "original text: "
Debug.Print 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.

Dim sbJwe As New ChilkatStringBuilder
success = sbJwe.Append("eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.")
success = sbJwe.Append("OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe")
success = sbJwe.Append("ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb")
success = sbJwe.Append("Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV")
success = sbJwe.Append("mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8")
success = sbJwe.Append("1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi")
success = sbJwe.Append("6UklfCpIMfIjf7iGdXKHzg.")
success = sbJwe.Append("48V1_ALb6US04U3b.")
success = sbJwe.Append("5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji")
success = sbJwe.Append("SdiwkIr3ajwQzaBtQD_A.")
success = sbJwe.Append("XFBoMYUZodetZdvTiFvSkQ")

success = jwe2.LoadJweSb(sbJwe)
If (success <> 1) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

' Provide the RSA private key for decryption.
success = jwe2.SetPrivateKey(0,rsaPrivKey)

' Decrypt.
originalPlaintext = jwe2.Decrypt(0,"utf-8")
If (jwe2.LastMethodSuccess <> 1) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

Debug.Print originalPlaintext