I am using Following Code: generateSignature(algorithmName, input, consumersecret,tokensecret);
public static String generateSignature(String algorithmName, String input, String consumerSecret, String tokenSecret) {
        Blob sig = Crypto.generateMac(algorithmName, Blob.valueOf(input), Blob.valueOf(consumerSecret + '&' + tokenSecret));
        String signature = EncodingUtil.base64encode(sig);
        System.debug('##### signature: ' + signature);
        return signature;
    }

But from this, I got the error when signature contains '+' plus operator. Please help to find the solution.