code: public static Signature generateSignature(AsymmetricAlgorithm asymmetricAlgorithm, DigestAlgorithm digestAlgorithm) {
  		try {
  			return Signature.getInstance(generateAlgorithm(asymmetricAlgorithm, digestAlgorithm));
  		} catch (NoSuchAlgorithmException e) {
  			throw new CryptoException(e);
  		}
  	}
docs: 生成签名对象，仅用于非对称加密
  
  @param asymmetricAlgorithm {@link AsymmetricAlgorithm} 非对称加密算法
  @param digestAlgorithm {@link DigestAlgorithm} 摘要算法
  @return {@link Signature}