B4X

Duplicate Java Verify RSA Signature

See more RSA Examples

Demonstrates how to duplicate a snippet of Java code that verifies an RSA signature. B4X

Dim success As Boolean = False

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

'  This example duplicates the following Java code:

'  import com.sun.org.apache.xml.internal.security.utils.Base64;  
'  import java.io.ByteArrayInputStream;  
'  import java.security.PublicKey;  
'  import java.security.Signature;  
'  import java.security.cert.CertificateFactory;  
'  import java.security.cert.X509Certificate;  
'  public class validateSazetak {  
'    public static void main(String[] args) {  
'    String signatureAlgorithm = "SHA256withRSA";  
'    String base64DataToBeSigned = "Hlp...LE4=";  
'    String base64Certificate = "MII...TlQ==";  
'    String base64Signature = "I00...pZA==";  
'    try {  
'        CertificateFactory cf;  
'        X509Certificate certificate = null;  
'        cf = CertificateFactory.getInstance("X.509");  
'        certificate = (X509Certificate) cf.generateCertificate(new 
'        ByteArrayInputStream(Base64.decode(base64Certificate)));  
'         
'        Signature signature = Signature.getInstance(signatureAlgorithm, "SunRsaSign");  
'        PublicKey pk = (PublicKey) certificate.getPublicKey();  
'        signature.initVerify(pk);  
'         
'        byte[] hashBytes = Base64.decode(base64DataToBeSigned);  
'        signature.update(hashBytes);  
'         
'        byte[] sigBytes = Base64.decode(base64Signature);  
'        boolean validity = signature.verify(sigBytes);  
'        System.out.println("Is valid signature:" + validity);  
'      } catch (Exception e) {  
'          System.out.println(e);  
'      }  
'  } 

Dim base64DataToBeSigned As String = "Hlp...LE4="
Dim base64Certificate As String = "MII...TlQ=="
Dim base64Signature As String = "I00...pZA=="

Dim cert As ChilkatCert
cert.Initialize("cert")
success = cert.LoadFromBase64(base64Certificate)
If success = False Then
    Log(cert.LastErrorText)
    Return
End If


Dim rsa As ChilkatRsa
rsa.Initialize

success = rsa.SetX509Cert(cert, False)
If success = False Then
    Log(rsa.LastErrorText)
    Return
End If


rsa.EncodingMode = "base64"
success = rsa.VerifyStringENC(base64DataToBeSigned, "sha256", base64Signature)
If success = False Then
    Log(rsa.LastErrorText)
    Return
End If


Log("Signature verified.")