Java

Create ECSDA Signature using Raw r and s Format (not ASN.1)

See more ECC Examples

Demonstrates how to create an ECDSA signature using the raw r/s format.

ECDSA signatures have two equal sized parts, r and s. There are two common formats for encoding the signature:

(a) Concatenating the raw byte array of r and s
(b) Encoding both into a structured ASN.1 / DER sequence.

This example demonstrates how to create a signature that is a byte array of r and s concatenated.

Note: This example requires Chilkat v9.5.0.97 or greater.

Chilkat2 Java

import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Ecc;
import com.chilkatsoft.chilkat2.PrivateKey;
import com.chilkatsoft.chilkat2.Prng;
import com.chilkatsoft.chilkat2.PublicKey;
import com.chilkatsoft.chilkat2.StringBuilder;

public class ChilkatExample {

    public static void main(String[] args) {
        // This example requires the Chilkat API to have been previously unlocked.
        // See Global Unlock Sample for sample code.

        // To create an ECDSA signature, the data first needs to be hashed.  Then the hash
        // is signed.

        StringBuilder sb = new StringBuilder();
        sb.append("The quick brown fox jumps over the lazy dog");
        String hash = sb.getHash("sha256", "base64", "utf-8");

        // Load the ECDSA key to be used for signing.
        PrivateKey privKey = new PrivateKey();
        try {
            privKey.loadPemFile("qa_data/ecc/secp256r1-key-pkcs8.pem");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        Prng prng = new Prng();
        Ecc ecdsa = new Ecc();

        // Produce a signature that is not ASN.1, but is instead the concatenation
        // of the raw r and s signature parts.
        // This feature was added in Chilkat v9.5.0.97
        ecdsa.setAsnFormat(false);

        String ecdsaSigBase64;
        try {
            ecdsaSigBase64 = ecdsa.signHashENC(hash, "base64", privKey, prng);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("ECDSA signature = " + ecdsaSigBase64);

        // -----------------------------------------------------------
        // Now let's verify the signature using the public key.

        PublicKey pubKey = new PublicKey();
        try {
            pubKey.loadFromFile("qa_data/ecc/secp256r1-pubkey.pem");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Note: When verifying, Chilkat will auto-detect the format for both kinds of ECDSA signatures (ASN.1 or binary r+s)
        int result = ecdsa.verifyHashENC(hash, ecdsaSigBase64, "base64", pubKey);
        if (result == 1) {
            System.out.println("Signature is valid.");
            return;
        }

        if (result == 0) {
            System.out.println("Signature is invalid.");
            return;
        }

        if (result < 0) {
            System.out.println(ecdsa.getLastErrorText());
            System.out.println("The VerifyHashENC method call failed.");
            return;
        }
    }
}