Public key encoding changes

Question

I've generated a public key using elliptic curves, but whenever I get the encoding of the key, it changes. I would like to use the encoding for a public address of a blockchain I am implementing. See below

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PublicKey;
import java.security.spec.ECGenParameterSpec;

class Scratch {
    public static void main(String[] args) throws Exception {
        KeyPairGenerator keyGen = KeyPairGenerator.getInstance("EC");
        ECGenParameterSpec ecSpec = new ECGenParameterSpec("secp256k1");
        keyGen.initialize(ecSpec);
        KeyPair kp = keyGen.generateKeyPair();

        PublicKey k = kp.getPublic();
        byte[] one = k.getEncoded();
        byte[] two = k.getEncoded();

        System.out.println(one);
        System.out.println(two);

    }
}

With output

[B@4eec7777
[B@3b07d329

Does anyone know why this is happening? My guess is that it is the expected behavior and I am just misunderstanding something fundamental here.

Answer 1

You are printing the memory address of the byte[], not the key itself. You can't "print" a byte array because it is binary data, you need to encode it somehow first. Hex and base64 are both good encodings for displaying binary data. For memory, other blockchain implementations like to use base58.

Here is an example using base64:

String b64Str = Base64.getEncoder().encodeToString(one);
System.out.println(b64Str);