@Override
    public String createLogoutParameter(String sessionId) {
        try {
            Signature signature = Signature.getInstance(DEFAULT_SIGNATURE_ALGORITHM);

            signature.initSign(this.privateKey);

            Base64.Encoder urlEncoder = Base64.getUrlEncoder();

            return sessionId + "." + ByteIterator.ofBytes(urlEncoder.encode(ByteIterator.ofBytes(sessionId.getBytes()).sign(signature).drain())).asUtf8String().drainToString();
        } catch (NoSuchAlgorithmException | InvalidKeyException e) {
            throw new IllegalStateException(e);
        }
    }
    
    @Override
    public String verifyLogoutParameter(String parameter) {
        String[] parts = parameter.split("\\.");
        if (parts.length != 2) {
            throw new IllegalArgumentException(parameter);
        }
        try {
            String localSessionId = ByteIterator.ofBytes(parts[0].getBytes()).asUtf8String().drainToString();
            Signature signature = Signature.getInstance(DEFAULT_SIGNATURE_ALGORITHM);

            signature.initVerify(this.certificate);
            signature.update(localSessionId.getBytes());

            Base64.Decoder urlDecoder = Base64.getUrlDecoder();

            if (!ByteIterator.ofBytes(urlDecoder.decode(parts[1].getBytes())).verify(signature)) {
                throw log.httpMechSsoInvalidLogoutMessage(localSessionId);
            }

            return localSessionId;
        } catch (NoSuchAlgorithmException | InvalidKeyException e) {
            throw new IllegalStateException(e);
        } catch (SignatureException e) {
            throw new IllegalArgumentException(parameter, e);
        }
    }