巨型整数运算问题，请大侠们帮忙啊

fly231

因为现在用RSA算法进行数字签名，里面的运算涉及到很大的数字，
比如（235^122），如果用一般的pow函数运算肯定溢出，不知道各位老大有什么好方法，在unix下的bc可以很快算出结果，不知道是怎么做的，哪里能找到他的源码啊，请各位大侠帮忙啊，小弟着俩天就要用了，我哭

flw

1，bc 的源码到 google 上去搜，保证找到一箩筐。
2，大数的运算可以自己编程序实现，你想一下小学二年级的时候老师是如何教你“多位数乘法”的，就知道了。

sprinklexu

2楼的话言简意赅哈

fly231

原帖由 "flw" 发表：
1，bc 的源码到 google 上去搜，保证找到一箩筐。
2，大数的运算可以自己编程序实现，你想一下小学二年级的时候老师是如何教你“多位数乘法”的，就知道了。

老大，能给一个bc源码的链接吗，我在google例搜索出来的都是没有关系的东东，自己可以做一个算法，而且能够实现，关键是效率啊，如果一个加密过程要几个小时谁还会用啊，我还是想看看bc的实现，他的效率很高啊，巨大的数字运算很快就出来结果了

fly231

我要在几天内完成这个工作，我自己认为要完成（4453^2234）这种巨型运算，而且保证效率，自己是无法实现了，只能借鉴前人的东西了，哪位大仙认为可以做到吗，但是unix下的bc确实可以啊，只用了2秒，就看到一大屏幕的数字出来了，请各位老大不要和我说让我自己实现了，我斗胆问一下老大自己能够实现吗，得罪得罪，只要告诉我可以查看的链接

lenovo

你看置顶的帖子，有一个科学计算的库。

win_hate

RSA 计算用的是模乘，那有象你这样算的？

fly231

[quote]原帖由 "win_hate"]RSA 计算用的是模乘，那有象你这样算的？[/quote 发表：

下面是转贴的rsa算法，你自己看一下吧，有没有我这样算的
The RSA algorithm was invented in 1978 by Ron Rivest, Adi Shamir, and Leonard Adleman.

Here's the relatively easy to understand math behind RSA public key encryption.

Find P and Q, two large (e.g., 1024-bit) prime numbers.

Choose E such that E is greater than 1, E is less than PQ, and E and (P-1)(Q-1) are relatively prime, which means they have no prime factors in common. E does not have to be prime, but it must be odd. (P-1)(Q-1) can't be prime because it's an even number.

Compute D such that (DE - 1) is evenly divisible by (P-1)(Q-1). Mathematicians write this as DE = 1 (mod (P-1)(Q-1)), and they call D the multiplicative inverse of E. This is easy to do -- simply find an integer X which causes D = (X(P-1)(Q-1) + 1)/E to be an integer, then use that value of D.

The encryption function is C = (T^E) mod PQ, where C is the ciphertext (a positive integer), T is the plaintext (a positive integer), and ^ indicates exponentiation. The message being encrypted, T, must be less than the modulus, PQ.

The decryption function is T = (C^D) mod PQ, where C is the ciphertext (a positive integer), T is the plaintext (a positive integer), and ^ indicates exponentiation.
Your public key is the pair (PQ, E). Your private key is the number D (reveal it to no one). The product PQ is the modulus (often called N in the literature). E is the public exponent. D is the secret exponent.

You can publish your public key freely, because there are no known easy methods of calculating D, P, or Q given only (PQ, E) (your public key). If P and Q are each 1024 bits long, the sun will burn out before the most powerful computers presently in existence can factor your modulus into P and Q.

win_hate

呵呵，

fly231

[quote]原帖由 "lenovo"]你看置顶的帖子，有一个科学计算的库。[/quote 发表：

谢谢，已经下载了库，正在找相关的函数，比较累，有没有熟悉的人指点一二，不胜感激