BASE64加密算法

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#include <stdio.h>#include <windows.h>char Chars[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890+=";int GetIndex(BYTE b){for (int i = 0; i < 64; i++){if (b == Chars[i]){return i;}}return 0;}VOID Base64Encrypt(BYTE* pScr, int nScrLen, BYTE* pDes, int& nDesLen){int nCount = nScrLen / 3;int i;for (i = 0; i < nCount; i++){pDes[i * 4] = Chars[(pScr[3 * i] & 252) >> 2];pDes[i * 4 + 1] = Chars[((pScr[3 * i] & 3) << 4) + ((pScr[3 * i + 1] & 240) >> 4)];pDes[i * 4 + 2] = Chars[((pScr[3 * i + 1] & 15) << 2) + ((pScr[3 * i + 2] & 192) >> 6)];pDes[i * 4 + 3] = Chars[pScr[3 * i + 2] & 63];}nDesLen = nCount * 4;nCount = nScrLen % 3;if (nCount == 1){pDes[i * 4] = Chars[(pScr[3 * i] & 252) >> 2];pDes[i * 4 + 1] = Chars[((pScr[3 * i] & 3) << 4)];nDesLen += 2;}else if (nCount == 2){pDes[i * 4] = Chars[(pScr[3 * i] & 252) >> 2];pDes[i * 4 + 1] = Chars[((pScr[3 * i] & 3) << 4) + ((pScr[3 * i + 1] & 240) >> 4)];pDes[i * 4 + 2] = Chars[((pScr[3 * i + 1] & 15) << 2)];nDesLen += 3;}}VOID Base64Decrypt(BYTE* pScr, int nScrLen, BYTE* pDes, int& nDesLen){int nCount = nScrLen / 4;int i;for (i = 0; i < nCount; i++){pDes[i * 3] = (GetIndex(pScr[i * 4]) << 2) + (GetIndex(pScr[i * 4 + 1]) >> 4);pDes[i * 3 + 1] = ((GetIndex(pScr[i * 4 + 1]) & 15) << 4) + (GetIndex(pScr[i * 4 + 2]) >> 2);pDes[i * 3 + 2] = ((GetIndex(pScr[i * 4 + 2]) & 3) << 6) + (GetIndex(pScr[i * 4 + 3]));}nDesLen = 3 * nCount;if (nScrLen % 4 == 2){pDes[i * 3] = (GetIndex(pScr[i * 4]) << 2) + (GetIndex(pScr[i * 4 + 1]) >> 4);nDesLen++;}else if (nScrLen % 4 == 3){pDes[i * 3] = (GetIndex(pScr[i * 4]) << 2) + (GetIndex(pScr[i * 4 + 1]) >> 4);pDes[i * 3 + 1] = ((GetIndex(pScr[i * 4 + 1]) & 15) << 4) + (GetIndex(pScr[i * 4 + 2]) >> 2);nDesLen += 2;}}int main(void){BYTE buff1[24] = { 0 };BYTE buff2[24] = { 0 };int nLen1 = 0;int nLen2 = 0;BYTE Str[] = "Hello a World";Base64Encrypt(Str, sizeof(Str), buff1, nLen1);Base64Decrypt(buff1, nLen1, buff2, nLen2);return 0;}
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