实验内容:编程实现RSA算法,要求有密钥生成、加密步骤和解密步骤。
实验操作步骤
1、密钥生成
(1)任选两个不同的大素数𝑝和𝑞,计算𝑛=𝑝𝑞,𝜑(𝑛)=(𝑝−1)(𝑞−1)。
计算n=p*q,fy(n)=(p-1)(q-1)
(2)任选一个大整数𝑒,满足gcd(𝑒,𝜑(𝑛))=1,𝑒为公钥PK。
(3)作为私钥SK的𝑑,应满足𝑑𝑒 𝑚𝑜𝑑 𝜑(𝑛)=1,即𝑑𝑒=𝑘𝜑(𝑛)+1,其中,𝑘≥1且是整数。
实验过程中,我发现当p和q取大整数时,计算d的过程很漫长,因此引入大整数幂取模算法,即蒙哥马利算法。当把mod N 转换为mod R时,a mod N需要转换为:aR mod N,aR称为整数a的蒙哥马利形式,对于加减法:aR±bR=(a±b)R,对于乘法,需要乘上R的逆元R’,即:((aR mod N)(bR mod N)mod N)R’=(aR)(bR)R’=(ab)RmodN。
(4)公开整数𝑛和𝑒,秘密保存𝑑。
2、加密步骤
将明文𝑚(𝑚<𝑛,是一个整数)加密成密文𝑐,加密算法为𝑐=𝐸(𝑚)=𝑚𝑒 𝑚𝑜𝑑 𝑛
3、解密步骤
将密文𝑐解密为明文𝑚,解密算法为𝑚=𝐷(𝑐)=𝑐𝑑 𝑚𝑜𝑑 𝑛
import math
from msvcrt import kbhit
import time
# 辗转相除法求a,b的最大公因数
def gcd(a, b):
k=0
while (1):
k=a%b
a=b
b=k
if(k==0):
break
return a
#扩展欧几里的算法计算 ax + by = 1中的x与y的整数解(a与b互质)
'''求解ax=1(mod b),就是求ax+by=1中x与y的整数解
求解乘法逆元d,(d*e=1 mod(fai),就是求d*e+fai*y=1的解'''
def ext_gcd(a, b):
if b == 0:
x1 = 1
y1 = 0
x=x1
y=y1
r = a
return r, x, y
else:
r, x1, y1 = ext_gcd(b, a % b)
x=y1
y = x1 - a // b * y1
return r, x, y
#蒙哥马利算法
def exp_mode(base, exponent, n):
bin_array = bin(exponent)[2:][::-1]
r = len(bin_array)
base_array = []
pre_base = base
base_array.append(pre_base)
for _ in range(r - 1):
next_base = (pre_base * pre_base) % n
base_array.append(next_base)
pre_base = next_base
a_w_b = __multi(base_array, bin_array, n)
return a_w_b % n
def __multi(array, bin_array, n):
result = 1
for index in range(len(array)):
a = array[index]
if not int(bin_array[index]):
continue
result *= a
result = result % n # 加快连乘的速度
return result
# 生成公钥私钥,p、q为两个超大质数
def gen_key(p, q):
n = p * q
fy = (p - 1) * (q - 1)
a = e
b = fy
r, x, y = ext_gcd(a, b)
# 计算出的x不能是负数,如果是负数,说明p、q、e选取失败,不过可以把x加上fy,使x为正数,才能计算。
if x < 0:
x = x + fy
d = x
print("d为-->",d)
# 返回: 公钥 私钥
return (n, e), (n, d)
# 加密 m是被加密的信息 加密成为c
def encrypt(m, pubkey):
n = pubkey[0]
e = pubkey[1]
c = exp_mode(m, e, n)
return c
# 解密 c是密文,解密为明文m
def decrypt(c, selfkey):
n = selfkey[0]
d = selfkey[1]
m = exp_mode(c, d, n)
return m
if __name__ == "__main__":
'''公钥私钥中用到的两个大质数p,q,都是1024位'''
#p = 106697219132480173106064317148705638676529121742557567770857687729397446898790451577487723991083173010242416863238099716044775658681981821407922722052778958942891831033512463262741053961681512908218003840408526915629689432111480588966800949428079015682624591636010678691927285321708935076221951173426894836169
#q = 144819424465842307806353672547344125290716753535239658417883828941232509622838692761917211806963011168822281666033695157426515864265527046213326145174398018859056439431422867957079149967592078894410082695714160599647180947207504108618794637872261572262805565517756922288320779308895819726074229154002310375209
p=eval(input("请输入大素数p:"))
q=eval(input("请输入与p互素的大素数q:"))
print("n为-->",p*q)
e=eval(input("请输入任意一个大整数e:"))
'''生成公钥私钥'''
pubkey, selfkey = gen_key(p, q)
#print("d为-->",d)
'''需要被加密的信息转化成数字,长度小于秘钥n的长度,如果信息长度大于n的长度,那么分段进行加密,分段解密即可。'''
#m = 1356205320457610288745198967657644166379972189839804389074591563666634066646564410685955217825048626066190866536592405966964024022236587593447122392540038493893121248948780525117822889230574978651418075403357439692743398250207060920929117606033490559159560987768768324823011579283223392964454439904542675637683985296529882973798752471233683249209762843835985174607047556306705224118165162905676610067022517682197138138621344578050034245933990790845007906416093198845798901781830868021761765904777531676765131379495584915533823288125255520904108500256867069512326595285549579378834222350197662163243932424184772115345
m=eval(input("请输入待加密的信息m:"))
print("待加密信息-->%s" % m)
'''信息加密,m被加密的信息,c是加密后的信息'''
c = encrypt(m, pubkey)
print("被加密后的密文-->%s" % c)
'''信息解密'''
d = decrypt(c, selfkey)
print("被解密后的明文-->%s" % d)
实验结果
(1)p=11,q=13,e=17,m=24
(2)p=885320963,q=238855417,e=65537,m=24
(3)p=106697219132480173106064317148705638676529121742557567770857687729397446898790451577487723991083173010242416863238099716044775658681981821407922722052778958942891831033512463262741053961681512908218003840408526915629689432111480588966800949428079015682624591636010678691927285321708935076221951173426894836169,q=144819424465842307806353672547344125290716753535239658417883828941232509622838692761917211806963011168822281666033695157426515864265527046213326145174398018859056439431422867957079149967592078894410082695714160599647180947207504108618794637872261572262805565517756922288320779308895819726074229154002310375209,e=65537,m=24