B4X Requires Chilkat v11.0.0+

Generate RSA Key and Sign a String

See more RSA Examples

Demonstrates how to generate a new RSA public/private key pair and use it to generate a signature for a string. The (binary) digital signature is returned as a hexidecimalized string. B4X

Dim success As Boolean = False

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

Dim rsa As ChilkatRsa
rsa.Initialize

'  Generate a 2048-bit RSA key.
Dim privKey As ChilkatPrivateKey
privKey.Initialize("privKey")
success = rsa.GenKey(2048, privKey)

rsa.UsePrivateKey(privKey)

'  Return the signature in hex.
rsa.EncodingMode = "hex"

Dim strData As String = "This is the string to be signed."

'  Sign the SHA256 hash of the string.
Dim hexSig As String = rsa.SignStringENC(strData, "sha256")

Log(hexSig)

'  Now verify the signature:
Dim pubKey As ChilkatPublicKey
pubKey.Initialize
privKey.ToPublicKey(pubKey)
rsa.UsePublicKey(pubKey)

success = rsa.VerifyStringENC(strData, "sha256", hexSig)
If success = True Then
    Log("Signature verified!")
Else
    Log(rsa.LastErrorText)
End If


'  Try it with an invalid signature:
success = rsa.VerifyStringENC(strData, "sha256", "not a valid sig")
If success = True Then
    Log("Signature verified!")
Else
    Log("Signature validation failed!")
End If


'  Try it with invalid data:
success = rsa.VerifyStringENC("Not the original data", "sha256", hexSig)
If success = True Then
    Log("Signature verified!")
Else
    Log("Signature validation failed!")
End If