LX3820

title: buuctf题解date: 2022-03-21 20:28:10categories:tags: 题解 [NCTF2019]childRSA以下是题目： 123456789101112131415161718192021from random import choicefrom Crypto.Util.number import isPrime, sieve_base as primesfrom flag import flagdef getPrime(bits): while True: n = 2 while n.bit_length() < bits: n *= choice(primes) if isPrime(n + 1): return n + 1e = 0x10001m = int.from_bytes(flag.encode(), 'big')p, q = [getPrime(2048) for _ in range(2)]n = p * ...

Easy RSA以下是题目： 123456789101112131415161718from math import gcdfrom random import randintfrom gmpy2 import next_primefrom Crypto.Util.number import getPrimefrom secret import flag##意思是将flag进行了加密，让你解出flagdef encrypt(c): p = getPrime(8) q = getPrime(8) e = randint(0, p * q) while gcd(e, (p - 1) * (q - 1)) != 1: e = int(next_prime(e)) return e, p, q, pow(ord(c), e, p * q)if __name__ == '__main__': print(list(map(encrypt, flag))) # [(12433, 149, 197, 104), (8147, ...

course one题目1：数字转ascill码 题意：将数字转为ascill码 所以脚本可得： 123456b=[]a=[99, 114, 121, 112, 116, 111, 123, 65, 83, 67, 73, 73, 95, 112, 114, 49, 110, 116, 52, 98, 108, 51, 125]for i in a: b+=chr(i)print(b)#['c', 'r', 'y', 'p', 't', 'o', '{', 'A', 'S', 'C', 'I', 'I', '_', 'p', 'r', '1', 'n', 't', '4', 'b&# ...

####二次残差 Quadratic Residues a^2^ $\equiv$ x mod p 即,a^2^>p时, (a^2^-x)是p的倍数 (当a^2^<p时, x = a^2^) $\therefore$x= a^2^-mp (a^2^ > p) 例如： 12345678910p=7a += 1 1^2 = 1 (mod 7) # 1<7, x=a^2=12^2 = 4 (mod 7) # 4<7, x=a^2=43^2 = 2 (mod 7) # 9>7, x=a^2-p*1=24^2 = 2 (mod 7) # 16>7, x=a^2-p*2=25^2 = 4 (mod 7) # 25>7, x=a^2-p*3=46^2 = 1 (mod 7) # 36>7, x=a^2-p*5=1# 1,2,4 are Quadratic Residue of 7 # 3,5,6 are Quadratic Non-Residue of 7 Legendre Symbol Euler 判别准则 对于 ...

RSA的算法：1.任意选取两个不同的大素数p和q计算乘积n=p$\times$q 利用欧拉函数求出与n互质的数的个数$\varphi$(n)=(p-1)$\times$(q-1) ==欧拉函数:== 欧拉函数的定义： 欧拉函数(Euler’s totient function),即为$\phi$(n),是小于 n 且与 n 互质的数的个数 例如$\varphi$(7)=6,因为与7互质的数有1，2，3，4，5，6。所以只要n为素数则$\varphi$(n)=n-1 2.任意选取一个大整数e满足gcd(e,$\phi$(n))=1,整数e用作==加密钥==（1<e<$\phi$(n)） 3确定解密钥d，满足(ed) mod $\varphi$(n) = 1,即ed = k $\times$$\varphi$(n) +1,k$\geq$1是一个任意整数 4.公开整数n和e，秘密保存d 5.将明文m加密为密文c的算m法为： c&#x ...