C的RSA密码算法实现
C写的，囧，网络课本上看过，对于我这种数学白痴怎么可能会？拖住wekooo要了公式，随便写写……
对于转ascii码的时候太囧，char最大到127，超过就变负数了，经常出乱码，太郁闷，后面改成unsigned char，在p=11，q=13的情况下可以成功转换a-z0-9的内容……
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#include<stdio.h>
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int gcd(int a, int b){
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return b==0?a:gcd(b,a%b);
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}
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int getE(int t, int n){
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int e = 2;
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while(e<n&&gcd(e,t)!=1)e++;
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return e;
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}
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int getD(int t, int e){
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int d = 1;
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while(((e*d)%t)!=1)d++;
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return d;
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}
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int pow(int x, int e, int n){
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int s = 1;
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while(e--){
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s*=x;
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s%=n;
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}
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return s;
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}
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unsigned char rsa(unsigned char c, int e, int n){
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return pow(c, e, n);
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}
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int main(){
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int p,q;
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int n;
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int e,d;
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int i;
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char filePath[100];
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unsigned char word[1000], en_word[1000], de_word[1000];
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FILE *fp,*fc;
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scanf("%d%d",&p,&q);
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n = p*q;
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e = getE((p-1)*(q-1),n);
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d = getD((p-1)*(q-1),e);
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scanf("%s",filePath);
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fp=fopen(filePath, "r");
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fc=fopen("encrypted.txt", "w");
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while(fscanf(fp,"%s",word)!=EOF){
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for(i=0; word[i]!='\0'; i++) en_word[i] = rsa(word[i], e, n);
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en_word[i] = '\0';
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fprintf(fc,"%s", en_word);
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}
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fclose(fp);
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fclose(fc);
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fp=fopen("encrypted.txt", "r");
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fc=fopen("decrypted.txt", "w");
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while(fscanf(fp,"%s",word)!=EOF){
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for(i=0; word[i]!='\0'; i++) de_word[i] = rsa(word[i], d, n);
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de_word[i] = '\0';
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fprintf(fc,"%s", de_word);
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}
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fclose(fp);
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fclose(fc);
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return 0;
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}
wekooo大牛说e一般是选的3，如果(p-1)*(q-1)不为3的倍数的话。
这里且先不管 = =。p、q输入质数且128<p*q<256为佳……
不然会出bug 囧rz ……
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