B4X

RSA Sign an Encoded Hash

See more RSA Examples

Demonstrates signing a hash (e.g., SHA256) provided as an encoded string (e.g., base64 or hex). 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 the private key for this cert: " & cert.SubjectCN)

'  Create data to be hashed and signed.
Dim bd As ChilkatBinData
bd.Initialize
Dim i As Int
For i = 0 To 100
    bd.AppendEncoded("000102030405060708090A0B0C0D0E0F", "hex")
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


'  We'll first compute the hash and then pass the encoded hash to be signed.
Dim sha256_base64 As String = bd.GetHash("sha256", "base64")
Log("sha256 hash in base64 format: " & sha256_base64)

'  Pass in the base64 hash and return a base64 signature.
rsa.EncodingMode = "base64"
Dim rsaSig_base64 As String = rsa.SignHashENC(sha256_base64, "sha256")
If success = False Then
    Log(rsa.LastErrorText)
    Return
End If


Log("RSA signature as base64: " & rsaSig_base64)