说明：  本次实验是基于广泛测试的公开加密库来实现数字签名服务。这里选择了 M2Crypto 加密库来实现，M2Crypto 加密库能够完整的支持 OpenSSL 库，所以会 更加方便点。而且这个库中包含有 RSA 非对称加密算法（M2Crypto.RSA），高级 的加密解密接口（M2Crypto.EVP）,还能操作 X.509 证书(M2Crypto.X509)。我们 可以先通过 M2Crypto 库里的模块来生成证书、公钥文件和私钥文件，后面再利 用生成的证书、私钥和公钥来实现加密解密及数字签名认证。
(This experiment is based on a widely tested public encryption library to implement digital signature services. Here is the choice The M2Crypto encryption library is implemented, and the M2Crypto encryption library can fully support the OpenSSL library, so it will It's more convenient. And this library contains a RSA asymmetric encryption algorithm (M2Crypto.RSA), high level The encryption and decryption interface (M2Crypto.EVP) can also operate the X.509 Certificate (M2Crypto.X509). We A certificate, a public key file, and a private key file can be generated by the modules of the M2Crypto repository first, and the later will be beneficial. The encrypted decryption and digital signature authentication are realized with the generated certificate, private key and public key.)