A short snippet to remember how to convert base64 encoded keys to their `java.security.PublicKey/PrivateKey` representation, using the i2p crypto library

keys.scala

import java.security.{KeyFactory, Security}
import java.util.Base64

import net.i2p.crypto.eddsa.EdDSASecurityProvider
import net.i2p.crypto.eddsa.spec.{EdDSANamedCurveTable, EdDSAPrivateKeySpec, EdDSAPublicKeySpec}
import net.i2p.crypto.eddsa.EdDSAEngine
import java.security.MessageDigest
import java.nio.charset.StandardCharsets

val pubKeyEdDSA = "e1ylCW17UIGCOrKH9zI6cceZxNe93sPsKpM0sm72bEQ="
val privKeyEdDSA = "jbcfwBz1WHFvyXp1lmUHOueiqMzQ1Q/fPgk+ppaHfkZ="

// Should be done in the app, somewhere, before calling `getInstance`
Security.insertProviderAt(new EdDSASecurityProvider, 0)

// Interesting part
val pub = Base64.getDecoder.decode(pubKeyEdDSA)
val priv = Base64.getDecoder.decode(privKeyEdDSA)

val spec = EdDSANamedCurveTable.ED_25519_CURVE_SPEC
val kf = KeyFactory.getInstance("EdDSA")

val pu = kf.generatePublic(new EdDSAPublicKeySpec(pub, spec))
val pr = kf.generatePrivate(new EdDSAPrivateKeySpec(priv, spec))
// Here we got the public and private key as java.security.* interface


// Quick snippet to generate a signature based on the key above
val msg = "hello".getBytes(StandardCharsets.UTF_8)

val sgr = new EdDSAEngine(MessageDigest.getInstance(spec.getHashAlgorithm))
sgr.initSign(pr)
sgr.update(msg)
val jcaSignature = Base64.getUrlEncoder.encodeToString(sgr.sign()).replace("=", "")