Java Requires Chilkat v11.0.0+

Verify an RSA Signature Against the Signed String

See more Apple Keychain Examples

Demonstrates how to validate an RSA Signature against the string that was signed. Chilkat2 Java

import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.PublicKey;
import com.chilkatsoft.chilkat2.Rsa;
import com.chilkatsoft.chilkat2.StringBuilder;

public class ChilkatExample {

    public static void main(String[] args) {
        // Create the same string we previously signed in this example:
        // RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

        StringBuilder sb = new StringBuilder();
        boolean crlfLineEnding = true;
        for (int i = 0; i <= 10; i++) {
            sb.appendLine("This is a test.", crlfLineEnding);
        }

        String base64_rsa_sig = "gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ==";

        // Get the public key to be used for signature verification.
        PublicKey pubKey = new PublicKey();
        try {
            pubKey.loadFromFile("rsaKeys/chilkat-rsa-2048.pem");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        Rsa rsa = new Rsa();
        try {
            rsa.usePublicKey(pubKey);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // 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.
        rsa.setCharset("utf-8");
        rsa.setEncodingMode("base64");
        String signedString = sb.getAsString();

        try {
            rsa.verifyStringENC(signedString, "sha256", base64_rsa_sig);
            System.out.println("Signature valid.");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            System.out.println("Signature invalid.");
        }
    }
}