0x00 前言

学校网络安全实验，虽然我对密码学真的不感冒，但是我们学院就是这么特别，网络工程也要学密码学，而且是几个学期反复教相同的东西，没错，就是你(XD university)。原理部分就下次再写了。

0x01 实验要求

实验要求1
给定素数p和q，公钥e，计算d
p=11; q=13; e=11; d=??
p=17; q=11; e=7;   d=??
p=5;   q=11; e=3;   d=??
实验要求2
根据自己计算出的公私钥对，以及p, q，设计程序，实现RSA的加密和解密
加密：输入明文、密钥，输出密文
解密：输入密文、密钥，输出明文
实验要求3
根据自己计算出的公私钥对，以及p, q，设计程序，实现RSA的签名和验证
签名：输入消息、密钥，输出签名消息
验证：输入签名消息、密钥，输出原文

0x02 代码与实现

1、计算d

def find_d(e, s):
    for d in range(s):  
        x = (e * d) % s
        if x == 1:
            return d
 
if __name__ == '__main__':
    p = input("what's your p ?")
    q = input("what's your q ?")
    e = int(input("what's your e ?"))
    s = (int(p)-1) * (int(q)-1)
    print(s)
    print(find_d(e, s))

2、加密与解密

import rsa
 
 
def str2_ascii_int(string1):
    xx = ""
    for i in string1:
        xx = xx + hex(ord(i))[2:]
    return int(xx, 16)
 
 
def ascii_int2str(num1):
    xx = hex(num1)[2:]
    i = 0
    sign_name = ""
    while i < len(xx) / 2:
        current_str = xx[2 * i:2 * i + 2]
        real = chr(int(current_str, 16))
        sign_name = sign_name + real
        i = i + 1
    return sign_name
 
 
def encryption(plaintext, e, n):
    cryptotext = pow(plaintext, e) % n
    return cryptotext
 
 
def decryption(cryptotext, d, n):
    plaintext = pow(cryptotext, d) % n
    return plaintext
 
 
# this part is mainly for signature, in the part, the public key will be used for decryption and the private key will be
# used for encryption, but why? Because the public key is open for everyone, and the private key is just for the owner.
# if you want anyone else to recognize you as xxx, you should offer the other one a signature ,because the signature is
# encrypted by private key, so no one else can get the same signature expect the loss of the private key.
if __name__ == '__main__':
    key = rsa.newkeys(32)
    n = key[1].n
    e = key[1].e
    d = key[1].d
    plaintext = input("what's your plaintext ?")
    print("the plaintext is : ", plaintext)
    cryototext = encryption(str2_ascii_int(plaintext), e, n)  # 用私钥加密，签名
    print("the cryptotext is : ", cryototext)
    recognize_name = ascii_int2str(decryption(cryototext, d, n))  # 用公钥解密，验证
    print(str(recognize_name))

3、签名与签名验证（我实在想吐槽这个，老师你就不能让我用hash吗，为什么要让我输出原文！！！！

注意：p*q 的值必须大于message的值，否则会出错，也就是说如果你用ascii来做的话，p=17, q = 11 那么message的值必须小于187，所以我这里就只选了一个字母来做验证）

import rsa
 
 
def str2_ascii_int(string1):
    xx = ""
    for i in string1:
        xx = xx + hex(ord(i))[2:]
    return int(xx, 16)
 
 
def ascii_int2str(num1):
    xx = hex(num1)[2:]
    i = 0
    sign_name = ""
    while i < len(xx) / 2:
        current_str = xx[2 * i:2 * i + 2]
        real = chr(int(current_str, 16))
        sign_name = sign_name + real
        i = i + 1
    return sign_name
 
 
def encryption(plaintext, e, n):
    cryptotext = pow(plaintext, e) % n
    return cryptotext
 
 
def decryption(cryptotext, d, n):
    plaintext = pow(cryptotext, d) % n
    return plaintext
 
 
# this part is mainly for signature, in the part, the public key will be used for decryption and the private key will be
# used for encryption, but why? Because the public key is open for everyone, and the private key is just for the owner.
# if you want anyone else to recognize you as xxx, you should offer the other one a signature ,because the signature is
# encrypted by private key, so no one else can get the same signature expect the loss of the private key.
if __name__ == '__main__':
    key = rsa.newkeys(16) # 这里的生成位数这么低是为了方便我自己计算，作为验证，实际使用请不要这么小
    n = key[1].n
    e = key[1].e
    d = key[1].d
    sig_name = input("what's your name ?")
    print("your name is : ", sig_name)
    signature = encryption(str2_ascii_int(sig_name), d, n)  # 用私钥加密，签名
    print("the signature is : ", signature)
    recognize_name = ascii_int2str(decryption(signature, e, n))  # 用公钥解密，验证
    print(str(recognize_name))

0x03 注意事项

其实这个实验真的很简单，理论部分你不懂也能做，但是这个实验最恶心的就是python中各种16进制，10进制字符串，消息字符串之间的各种转变，我花时间最多的反而是这个，加解密和签名基本就十几分钟就写好了，当然也是因为这次实验本身不带有密钥生成部分的内容，否则还是要花一些时间的。

0x04 后记与总结

密码学毫无疑问是安全通信中基础中的基础，也是重中之重，然而如何生成安全密钥，管理密钥和防止密钥泄露才是一个工作人员应该注意的点之一。之后有时间会更新关于密钥生成以及密钥管理中的相关内容，有写得不对的地方还请指出。