code: public static PublicKey generatePublicKey(String algorithm, KeySpec keySpec) {
  		if (null == keySpec) {
  			return null;
  		}
  		algorithm = getAlgorithmAfterWith(algorithm);
  		try {
  			return getKeyFactory(algorithm).generatePublic(keySpec);
  		} catch (Exception e) {
  			throw new CryptoException(e);
  		}
  	}
docs: 生成公钥，仅用于非对称加密<br>
  算法见：https://docs.oracle.com/javase/7/docs/technotes/guides/security/StandardNames.html#KeyFactory
  
  @param algorithm 算法
  @param keySpec {@link KeySpec}
  @return 公钥 {@link PublicKey}
  @since 3.1.1