PureBasic

JWE using "dir" Direct use of Shared Symmetric Key

See more JSON Web Encryption (JWE) Examples

Demonstrates how to create a JWE using the "dir" alg -- which is to directly use a shared symmetric key.

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

PureBasic

IncludeFile "CkJwe.pb"
IncludeFile "CkJsonObject.pb"

Procedure ChilkatExample()

    success.i = 0

    ; 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.s = "Live long and prosper."

    jwe.i = CkJwe::ckCreate()
    If jwe.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; First build the JWE Protected Header..
    jweProtHdr.i = CkJsonObject::ckCreate()
    If jweProtHdr.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkJsonObject::ckAppendString(jweProtHdr,"alg","dir")
    CkJsonObject::ckAppendString(jweProtHdr,"enc","A128GCM")

    ; Don't forget to actually provide the protected header to the JWE object:
    CkJwe::ckSetProtectedHeader(jwe,jweProtHdr)

    ; The JWE is to use 128-bit AES GCM encryption as specified by the "enc" parameter.
    ; Given that the "alg" = "dir", we are to directly specify the AES GCM key.
    ; (It is assumed that the decrypting side also has knowledge of the direct key to be used..)

    ; Our key will be these 16 hex bytes: 000102030405060708090A0B0C0D0E0F

    ; The SetWrappingKey method is also used for "dir" direct keys.
    ; However, if there are multiple recipients, they must all share the same CEK (Content Encryption Key),
    ; which is specified by calling SetWrappingKey with an index of 0.

    recipientIndex.i = 0
    CkJwe::ckSetWrappingKey(jwe,recipientIndex,"000102030405060708090A0B0C0D0E0F","hex")

    ; Encrypt and return the JWE:
    strJwe.s = CkJwe::ckEncrypt(jwe,plaintext,"utf-8")
    If CkJwe::ckLastMethodSuccess(jwe) <> 1
        Debug CkJwe::ckLastErrorText(jwe)
        CkJwe::ckDispose(jwe)
        CkJsonObject::ckDispose(jweProtHdr)
        ProcedureReturn
    EndIf

    ; Show the JWE we just created:
    Debug strJwe

    ; Decrypt the JWE.
    jwe2.i = CkJwe::ckCreate()
    If jwe2.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkJwe::ckLoadJwe(jwe2,strJwe)
    If success <> 1
        Debug CkJwe::ckLastErrorText(jwe2)
        CkJwe::ckDispose(jwe)
        CkJsonObject::ckDispose(jweProtHdr)
        CkJwe::ckDispose(jwe2)
        ProcedureReturn
    EndIf

    CkJwe::ckSetWrappingKey(jwe2,0,"000102030405060708090A0B0C0D0E0F","hex")

    ; Decrypt.
    originalPlaintext.s = CkJwe::ckDecrypt(jwe2,0,"utf-8")
    If CkJwe::ckLastMethodSuccess(jwe2) <> 1
        Debug CkJwe::ckLastErrorText(jwe2)
        CkJwe::ckDispose(jwe)
        CkJsonObject::ckDispose(jweProtHdr)
        CkJwe::ckDispose(jwe2)
        ProcedureReturn
    EndIf

    Debug "original text: "
    Debug originalPlaintext

    ; Sample output:
    ; eyJhbGciOiJkaXIiLCJlbmMiOiJBMTI4R0NNIn0..20HX5Huc7f1nQC4pBUtiCQ.axFZIxtZy5j0ifJQUzGXLKIpsBuxJA.eBrOC-NrsreN6JeGuOPk1g
    ; original text: 
    ; Live long and prosper.


    CkJwe::ckDispose(jwe)
    CkJsonObject::ckDispose(jweProtHdr)
    CkJwe::ckDispose(jwe2)


    ProcedureReturn
EndProcedure