code: public String sign(String message) {
  		try {
  			final byte[] signature = signer.sign(message.getBytes(charsetName));
  			return new String(Base64.encodeBase64(signature, false));
  		} catch (UnsupportedEncodingException e) {
  			throw new SignatureException("unsupported encoding: charsetName=" + charsetName, e);
  		}
  	}
docs: Signs a message.
  
  @param message the message to sign
  @return a base64 encoded version of the signature