(PureBasic) RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature.

Chilkat PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkCert.pb"
IncludeFile "CkPublicKey.pb"
IncludeFile "CkPrivateKey.pb"
IncludeFile "CkRsa.pb"

Procedure ChilkatExample()

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

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

    ; Load the private key from an RSA .key file:
    success.i = CkPrivateKey::ckLoadPemFile(privKey,"privateKey.key")
    If success <> 1
        Debug CkPrivateKey::ckLastErrorText(privKey)
        CkPrivateKey::ckDispose(privKey)
        ProcedureReturn
    EndIf

    privKeyXml.s
    ; Get the private key in XML format:
    privKeyXml = CkPrivateKey::ckGetXml(privKey)

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

    ; Import the private key into the RSA component:
    success = CkRsa::ckImportPrivateKey(rsa,privKeyXml)
    If success <> 1
        Debug CkRsa::ckLastErrorText(rsa)
        CkPrivateKey::ckDispose(privKey)
        CkRsa::ckDispose(rsa)
        ProcedureReturn
    EndIf

    ; Create the signature as a hex string:
    CkRsa::setCkEncodingMode(rsa, "hex")

    strData.s = "This is the string to be signed."

    ; Sign the string using the sha-1 hash algorithm.
    ; Other valid choices are "md2", "sha256", "sha384",
    ; "sha512", and "md5".
    hexSig.s = CkRsa::ckSignStringENC(rsa,strData,"sha-1")

    Debug hexSig

    ; Load a digital certificate from a .cer file:
    cert.i = CkCert::ckCreate()
    If cert.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkCert::ckLoadFromFile(cert,"myCert.cer")
    If success <> 1
        Debug CkCert::ckLastErrorText(cert)
        CkPrivateKey::ckDispose(privKey)
        CkRsa::ckDispose(rsa)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    pubKey.i

    pubKey = CkCert::ckExportPublicKey(cert)

    ; Now verify using a separate instance of the RSA object:
    rsa2.i = CkRsa::ckCreate()
    If rsa2.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Import the public key into the RSA object:
    success = CkRsa::ckImportPublicKey(rsa2,CkPublicKey::ckGetXml(pubKey))
    If success <> 1
        Debug CkRsa::ckLastErrorText(rsa2)
        CkPrivateKey::ckDispose(privKey)
        CkRsa::ckDispose(rsa)
        CkCert::ckDispose(cert)
        CkRsa::ckDispose(rsa2)
        ProcedureReturn
    EndIf

    CkPublicKey::ckDispose(pubKey)

    ; The signature is a hex string, so make sure the EncodingMode is correct:
    CkRsa::setCkEncodingMode(rsa2, "hex")

    ; Verify the signature:
    success = CkRsa::ckVerifyStringENC(rsa2,strData,"sha-1",hexSig)
    If success <> 1
        Debug CkRsa::ckLastErrorText(rsa2)
        CkPrivateKey::ckDispose(privKey)
        CkRsa::ckDispose(rsa)
        CkCert::ckDispose(cert)
        CkRsa::ckDispose(rsa2)
        ProcedureReturn
    EndIf

    Debug "Success."


    CkPrivateKey::ckDispose(privKey)
    CkRsa::ckDispose(rsa)
    CkCert::ckDispose(cert)
    CkRsa::ckDispose(rsa2)


    ProcedureReturn
EndProcedure