B4X

RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

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Demonstrates how RSA sign the utf-8 byte representation of a string to get the signature in base64 format. B4X

Dim success As Boolean = False

'  Assuming the smartcard/USB token is installed with the correct drivers from the manufacturer,
'  this code can work on multiple platforms including Windows, MacOS, Linux, and iOS.

'  Chilkat automatically detects and determines the way in which the HSM is used,
'  which can be by PKCS11, Apple Keychain, Microsoft CNG / Crypto API, or ScMinidriver.

Dim cert As ChilkatCert
cert.Initialize("cert")

'  Set the token/smartcard PIN prior to loading.
cert.SmartCardPin = "123456"

'  Specify the certificate by its common name.
success = cert.LoadFromSmartcard("cn=chilkat-rsa-2048")
If success = False Then
    Log(cert.LastErrorText)
    Return
End If


Log("Signing with cert: " & cert.SubjectCN)

'  Create a string to be hashed and signed.
Dim sb As ChilkatStringBuilder
sb.Initialize
Dim crlfLineEnding As Boolean = True
Dim i As Int
For i = 0 To 10
    sb.AppendLine("This is a test.", crlfLineEnding)
Next

Dim rsa As ChilkatRsa
rsa.Initialize

'  Use the certificate's private key for signing.
success = rsa.SetX509Cert(cert, True)
If success = False Then
    Log(rsa.LastErrorText)
    Return
End If


'  Sign the SHA-256 hash of the utf-8 byte representation of the contents of sb
'  Return the signature in base64 format.
rsa.EncodingMode = "base64"
rsa.Charset = "utf-8"
Dim stringToSign As String = sb.GetAsString
Dim sigBase64 As String = rsa.SignStringENC(stringToSign, "sha256")
If rsa.LastMethodSuccess = False Then
    Log(rsa.LastErrorText)
    Return
End If


Log("RSA signature as base64: " & sigBase64)