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仙剑4音乐加密解密代码

仙剑4的音乐为SMP格式,由MP3格式加密而来。
在mayafei大神的笔记《仙剑奇侠传4》SMP音乐解密部分研究(附源代码)基础上,我研究了加密算法,下面给出加密和解密的C语言代码。

注意:仙剑4的MP3解码功能较弱,建议将加密前的MP3先用格式工厂一类的软件重新转换过。

解密代码

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#include<stdio.h>
#include<stdlib.h>
#include<string.h>

unsigned int key[] = {0x706D6156, 0x2E657269, 0x204A2E43, 0x53207461}; //"Vampire.C.J at SoftStar..."

//Decoding Part, see http://www.tuicool.com/articles/Mv63Yv
#define DELTA 0x9e3779b9
#define MX (((z>>5^y<<2) + (y>>3^z<<4)) ^ ((sum^y) + (key[(p&3)^e] ^ z)))
void btea(unsigned int *v, int n) {
unsigned int y, z, sum;
unsigned int p, rounds, e;
rounds = 6 + 52/n;
sum = rounds*DELTA;
y = v[0];
do {
e = (sum >> 2) & 3;
for (p=n-1; p>0; p--) {
z = v[p-1];
y = v[p] -= MX;
}
z = v[n-1];
y = v[0] -= MX;
} while ((sum -= DELTA) != 0);
}

void decrypt(char *input, char *output)
{
FILE *fin = fopen(input, "rb");
fseek(fin, 0, 2);
int flen = ftell(fin);
fseek(fin, 0, 0); //get file length
char *buf = (char*)malloc(flen);
fread(buf, flen, 1, fin);
fclose(fin);
unsigned int *cipher = (unsigned int*)(buf + 0x80);
btea(cipher, 0x400); //get index data
int pos = cipher[3]; //music data offset
int len = cipher[4] / 4;//music data length
unsigned int *music = (unsigned int*)(buf + pos);
btea(music, len);
FILE *fout = fopen(output, "wb");
fwrite(music, sizeof(int) * len, 1, fout);
fclose(fout);
free(buf);
}

int main(int argc, char *argv[])
{
for(int i=1;i<argc;i++)
{
char *s = argv[i];
int n = strlen(s);
char *t = (char*)malloc(n + 1);
strcpy(t, s);
strcpy(t + n - 3, "mp3"); //change "smp" to "mp3"
decrypt(s, t);
free(t);
}
}

加密代码

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#include<stdio.h>
#include<stdlib.h>
#include<string.h>

unsigned int key[] = {0x706D6156, 0x2E657269, 0x204A2E43, 0x53207461};
unsigned int hash_table[256];

//Coding Part, see http://www.tuicool.com/articles/Mv63Yv
#define DELTA 0x9e3779b9
#define MX (((z>>5^y<<2) + (y>>3^z<<4)) ^ ((sum^y) + (key[(p&3)^e] ^ z)))

void btea(unsigned int *v, int n) {
unsigned int y, z, sum;
unsigned int p, rounds, e;
rounds = 6 + 52/n;
sum = 0;
z = v[n-1];
do {
sum += DELTA;
e = (sum >> 2) & 3;
for (p=0; p<n-1; p++) {
y = v[p+1];
z = v[p] += MX;
}
y = v[0];
z = v[n-1] += MX;
} while (--rounds);
}

//put the file "hash_table" in the work directory
void read_hash_table()
{
FILE* fp=fopen("hash_table","rb");
fread(hash_table, sizeof(int), sizeof(hash_table), fp);
fclose(fp);
}

unsigned int hash(char *s) //hash(crc-like) of filename (**.mp3)
{
unsigned int i, init = 0;
char v7;
for(i=0;i<4;i++)
{
init <<= 8;
init |= s[i];
}
s+=4;
v7 = *s;
for ( i = ~init; v7; ++s )
{
i = hash_table[i >> 24] ^ (v7 | (i << 8));
v7 = s[1];
}
return ~i;
}

/*
Ex: If encrypted file's name is "P01-1.smp", then the string to be hashed is "p01-1.mp3"
*/
unsigned int hash_filename(char *path)
{
int n = strlen(path);
int slash;
for(slash=n-1;slash>=0;slash--)
{
if(path[slash]=='/'||path[slash]=='\\')
break;
}
n = n - slash - 1;
path += slash + 1;
char filename[30];
for(int i=0;i<n;i++)
{
if(path[i]>='A'&&path[i]<='Z') //lower
filename[i]=path[i]-'A'+'a';
else
filename[i]=path[i];
}
filename[n]=0;
strcat(filename, ".mp3");
unsigned int h = hash(filename);
return h;
}

#define FLAG_SIZE 0x20
#define INDEX_SIZE 0x400
void encrypt(char *input, char *output)
{
FILE *fin = fopen(input, "rb");
fseek(fin, 0, 2);
int flen = ftell(fin) / sizeof(int) + 1; //pad to multiple of sizeof int
fseek(fin, 0, 0);
unsigned int *music = (unsigned int*)calloc(flen, sizeof(int));
fread(music, flen, sizeof(int), fin);
fclose(fin);
btea(music, flen);

unsigned int flag[FLAG_SIZE] = {0};
flag[0] = 0x1a545352;
flag[3] = 0x100080;
flag[4] = 0x8000;
flag[1] = flag[5] = flag[8] = 1;
flag[2] = flag[7] = 0x80;

unsigned int index[INDEX_SIZE] = {0};
index[0] = hash_filename(output);
index[1] = 0x10005;
index[3] = 0x10080;
index[4] = index[5] = flen * sizeof(int);
index[7] = 1; //important
btea(index, INDEX_SIZE);

unsigned int pad[0x3c00] = {0};

char filename[30];
strcpy(filename,output);
strcat(filename,".smp");
FILE *fout = fopen(filename, "wb");
fwrite(flag, sizeof(int), FLAG_SIZE, fout);
fwrite(index, sizeof(int), INDEX_SIZE, fout);
fwrite(pad, sizeof(int), 0x3c00, fout);
fwrite(music, sizeof(int), flen, fout);
fclose(fout);
free(music);
}

int main(int argc, char *argv[])
{
read_hash_table();
char tmp[30];
for(int i=1;i<argc;i++)
{
printf("%s -> ___.smp ( <20 chars)\n", argv[i]);
scanf("%s", tmp);
encrypt(argv[i], tmp);
}
}

文件hash_table进行base64编码后的文本:

1
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