@Override
    protected byte[] engineSign() throws SignatureException {
        final NativeRef.EVP_MD_CTX ctxLocal = ctx;
        if (key == null) {
            // This can't actually happen, but you never know...
            throw new SignatureException("No key provided");
        }
        byte[] sig = NativeCrypto.EVP_DigestSign(ctxLocal, buffer.array(), 0, buffer.size());
        buffer.reset();
        return sig;
    }
The current OpenSSL key we're operating on.
common/src/main/java/org/conscrypt/OpenSslSignatureEdDsa.java