[古典密碼]:Caesar cipher(凱撒密碼)
阿新 • • 發佈:2018-12-26
非常簡單的訊息編碼方式,僅僅是將字母后移3位,而X Y Z右移就回到A B C.
加密的話就是簡單的加三取模即可;解密就是其反過程。
C++實現如下:
#include#include#includeusing namespace std; string nencrypted = { "Things are not always what they see" }; string ncrypted; void encrypt(string &unencrypted,string &encrypted) { encrypted.resize(unencrypted.size()); for (int i = 0;i < unencrypted.size();i++) { if ((int)unencrypted[i]>64 && (int)unencrypted[i] < 91) { encrypted[i] = (char)((((int)unencrypted[i] - 65 + 3) % 26) + 65);//減去65+3取模可得到後移三位的ascii(大寫) } else if ((int)unencrypted[i] > 96 && (int)unencrypted[i] < 123) { encrypted[i] = (char)((((int)unencrypted[i] - 97 + 3) % 26) + 97);//減去97+3取模可得到後移三位的ascii(小寫) } else { encrypted[i] = unencrypted[i]; } } } void decrypt(string &encrypted, string &decrypted) { decrypted.resize(encrypted.size()); for (int i = 0;i < encrypted.size();i++) { if ((int)encrypted[i]>64 && (int)encrypted[i] < 91) { decrypted[i] = (char)((((int)encrypted[i] - 65 - 3 + 26) % 26) + 65);//減去65-3取模可得到前移三位的ascii(大寫) //加26使其非負 } else if ((int)encrypted[i] > 96 && (int)encrypted[i] < 123) { decrypted[i] = (char)((((int)encrypted[i] - 97 - 3 + 26) % 26) + 97);//減去97-3取模可得到前移三位的ascii(小寫)//加26使其非負 } else { decrypted[i] = encrypted[i]; } } } int main() { encrypt(nencrypted, ncrypted); cout << ncrypted << endl; decrypt(ncrypted, nencrypted); cout << nencrypted << endl; return 0; }