(PureBasic) RSA Sign Binary Data and Verify (Recover the Original Data)

Demonstrates how to RSA sign binary data and then verify/recover the original data.

Note: This example uses methods introduced in Chilkat v9.5.0.77.

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IncludeFile "CkBinData.pb"
IncludeFile "CkPublicKey.pb"
IncludeFile "CkPrivateKey.pb"
IncludeFile "CkRsa.pb"

Procedure ChilkatExample()

    ; This example requires the Chilkat API to have been previously unlocked.
    ; See Global Unlock Sample for sample code.

    ; Load an RSA private key for signing.
    privKey.i = CkPrivateKey::ckCreate()
    If privKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success.i = CkPrivateKey::ckLoadEncryptedPemFile(privKey,"qa_data/pem/rsa_passwd.pem","passwd")
    If success <> 1
        Debug CkPrivateKey::ckLastErrorText(privKey)
        CkPrivateKey::ckDispose(privKey)
        ProcedureReturn
    EndIf

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

    CkRsa::ckImportPrivateKeyObj(rsa,privKey)

    ; We have some binary data (in hex) to sign
    originalData.s = "0102030405060708090A"
    bd.i = CkBinData::ckCreate()
    If bd.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkBinData::ckAppendEncoded(bd,originalData,"hex")

    ; If successful, the contents of bd are replaced with the RSA signature.
    success = CkRsa::ckOpenSslSignBd(rsa,bd)
    If success <> 1
        Debug CkRsa::ckLastErrorText(rsa)
        CkPrivateKey::ckDispose(privKey)
        CkRsa::ckDispose(rsa)
        CkBinData::ckDispose(bd)
        ProcedureReturn
    EndIf

    ; Show the RSA signature in base64
    Debug CkBinData::ckGetEncoded(bd,"base64")

    ; ------------------------------------------
    ; Get the public key from the private key
    pubKey.i = CkPrivateKey::ckGetPublicKey(privKey)

    ; Verify the signature and extract the original data.
    rsa2.i = CkRsa::ckCreate()
    If rsa2.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkRsa::ckImportPublicKeyObj(rsa2,pubKey)

    bVerified.i = CkRsa::ckOpenSslVerifyBd(rsa2,bd)
    Debug "signature verified: " + Str(bVerified)

    ; Show the original data:
    Debug "original data: " + CkBinData::ckGetEncoded(bd,"hex")

    CkPublicKey::ckDispose(pubKey)



    CkPrivateKey::ckDispose(privKey)
    CkRsa::ckDispose(rsa)
    CkBinData::ckDispose(bd)
    CkRsa::ckDispose(rsa2)


    ProcedureReturn
EndProcedure