(PowerBuilder) Verify an RSA Signature Against the Signed String

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Demonstrates how to validate an RSA Signature against the string that was signed.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

integer li_rc
oleobject loo_Sb
integer li_CrlfLineEnding
integer i
string ls_Base64_rsa_sig
oleobject loo_PubKey
integer li_Success
oleobject loo_Rsa
string ls_SignedString

// Create the same string we previously signed in this example: 
// RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

loo_Sb = create oleobject
// Use "Chilkat_9_5_0.StringBuilder" for versions of Chilkat < 10.0.0
li_rc = loo_Sb.ConnectToNewObject("Chilkat.StringBuilder")
if li_rc < 0 then
    destroy loo_Sb
    MessageBox("Error","Connecting to COM object failed")
    return
end if
li_CrlfLineEnding = 1

for i = 0 to 10
    loo_Sb.AppendLine("This is a test.",li_CrlfLineEnding)
next

ls_Base64_rsa_sig = "gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ=="

// Get the public key to be used for signature verification.
loo_PubKey = create oleobject
// Use "Chilkat_9_5_0.PublicKey" for versions of Chilkat < 10.0.0
li_rc = loo_PubKey.ConnectToNewObject("Chilkat.PublicKey")

li_Success = loo_PubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem")
if li_Success = 0 then
    Write-Debug loo_PubKey.LastErrorText
    destroy loo_Sb
    destroy loo_PubKey
    return
end if

loo_Rsa = create oleobject
// Use "Chilkat_9_5_0.Rsa" for versions of Chilkat < 10.0.0
li_rc = loo_Rsa.ConnectToNewObject("Chilkat.Rsa")

loo_Rsa.ImportPublicKeyObj(loo_PubKey)

// Verify the string against the signature.
// We signed the utf-8 byte representation of the string, so we must indicate
// to also validate against the utf-8 byte representation.
loo_Rsa.Charset = "utf-8"
loo_Rsa.EncodingMode = "base64"
ls_SignedString = loo_Sb.GetAsString()
li_Success = loo_Rsa.VerifyStringENC(ls_SignedString,"sha256",ls_Base64_rsa_sig)

if li_Success = 0 then
    Write-Debug loo_Rsa.LastErrorText
    Write-Debug "Signature invalid."
else
    Write-Debug "Signature valid."
end if



destroy loo_Sb
destroy loo_PubKey
destroy loo_Rsa