实用数字签名的步骤

（1）发送方使用MD5算法对通信内容进行计算，获得一个固定长度的信息摘要；

（2）发送方用自己的私钥加密生成的信息生成发送方的数字签名，发送方把这个数字签名作为发送信息的附件和明文信息，一同用接收方的公钥进行加密，将加密后的密文一同发送给接收方；

（3）接收方首先把接收到的密文用自己的私钥解密，得到明文信息和数字签名，再用发送方的公钥对数字签名进行解密，然后使用相同的单向散列算法来计算解密得到的明文信息，得到信息摘要；对比计算出来的信息摘要和发送方发送过来的信息摘要是否一致

思考：

（1）请分别选择文件test-1.txt和test_picture.bmp作为通讯内容，分别记录全过程用时，并对比一下；

（2）如果所发送的内容数据量非常大，上述方案中的效率不能满足要求，请考虑一下如何解决这个问题。-Practical steps digital signature

( A ) the sender uses the MD5 algorithm to calculate the content of communications , access to a fixed-length message digest　

( 2 ) the sender　s private key encryption with their own information generated by the sender generates a digital signature , the digital signature of the sender of the message as an attachment and send plaintext , together with the recipient　s public key to encrypt the encrypted sent along with the ciphertext to the recipient　

( 3 ) First, the recipient receives the ciphertext with his private key to decrypt , get the plaintext and the digital signature , then the sender　s public key to decrypt the digital signature , and then using the same one-way hash algorithm to calculate decrypted plaintext information, to receive message digest　 comparing the calculated message digest and the information sent from the sender summary is consistent

Reflections :

( 1 ) Please select the file test-1.txt respectively and test_pictur