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  1. #include <stdio.h>
  2. #include <memory.h>
  3.  
  4. int myrand(int *seed){
  5. 	int tmp;
  6. 	tmp = ((*seed * 257 >> 8) + *seed * 97) + 23 ^ -1496474763;
  7. 	*seed = tmp >> 16 & 65535 | tmp << 16;
  8. 	return *seed & 32767;
  9. }
  10.  
  11. //           0 : success!
  12. // -2147483647 : wrong header
  13. // -2147483646 : wrong checksum
  14. int decrypt(char *a) {
  15. 	int r, counter, ret;
  16. 	char *a_header, *a_body;
  17. 	int flags[64], seed, i, s;
  18. 	char *target;
  19. 	int check_sum,check_xor;
  20. 	ret = -2147483647;
  21. 	a_header = a;
  22. 	a_body = a + 16;
  23. 	if (strcmp(a_header + 0, "BSE 1.0")) return ret;
  24. 	if (*(short *)(a_header + 8) != 256) return ret;
  25. 	memset(flags, 0, 64 * 4);
  26. 	seed = *(long *)(a_header + 12);
  27. 	counter = 0;
  28. 	do {
  29. 		r = myrand(&seed);
  30. 		i = r & 64 - 1;
  31. 		while (flags[i]){
  32. 			i = i + 1 & 64 - 1;
  33. 		}
  34. 		r = myrand(&seed);
  35. 		s = r & 7;
  36. 		target = (a_body + 0) + i;
  37. 		r = myrand(&seed);
  38. 		switch(r & 1){
  39. 		case 0:
  40. 			r = myrand(&seed);
  41. 			r = (*target & 255) - r & 255;
  42. 			*target = r >> s | r << 8 - s;  // rotate shift right
  43. 			break;
  44. 		case 1:
  45. 			r = myrand(&seed);
  46. 			r = (*target & 255) - r & 255;
  47. 			*target = r << s | r >> 8 - s;  // rotate shift left
  48. 			break;
  49. 		}
  50. 		flags[i] = 1;  // done
  51. 		counter = counter + 1;
  52. 	} while (counter < 64);
  53. 	check_sum = 0;
  54. 	check_xor = 0;
  55. 	target = a_body + 0;
  56. 	counter = 0;
  57. 	do {
  58. 		check_sum = check_sum + (target[counter] & 255);
  59. 		check_xor = check_xor ^ (target[counter] & 255);
  60. 		counter = counter + 1;
  61. 	} while (counter < 64);
  62. 	ret =
  63. 		(a_header[10] & 255) == (check_sum & 255) &&
  64. 		(a_header[11] & 255) == (check_xor & 255) ?
  65. 			0 : -2147483646;
  66. 	return ret;
  67. }
  68.  
  69. int main(void) {
  70. 	int ret, i;
  71. 	unsigned char a[] = {
  72. 		0x42, 0x53, 0x45, 0x20, 0x31, 0x2e, 0x30, 0x00, 0x00, 0x01, 0xe0, 0xda,
  73. 		0xc9, 0xa5, 0x6d, 0x70, 0x20, 0xed, 0x53, 0x38, 0x7d, 0x95, 0xe3, 0x03,
  74. 		0x2c, 0xbe, 0x10, 0xd9, 0x42, 0x70, 0x09, 0x16, 0xa6, 0x77, 0xcd, 0x8f,
  75. 		0x80, 0x18, 0xdc, 0x3b, 0xd8, 0xf4, 0x22, 0x9e, 0xa5, 0x87, 0x03, 0x18,
  76. 		0xac, 0x3c, 0x71, 0x1f, 0xa0, 0xd5, 0x1f, 0x68, 0x1e, 0x06, 0x95, 0x46,
  77. 		0x4e, 0xc0, 0x18, 0x17, 0x53, 0x78, 0xd7, 0x3a, 0x53, 0x70, 0x9b, 0x52,
  78. 		0x82, 0x81, 0xe5, 0x01, 0xe9, 0xa8, 0xe0, 0x79, 0xce, 0x43, 0x74, 0xa4,
  79. 		0x01, 0xce, 0x15, 0x91, 0x4e, 0x20, 0xd5, 0xa3, 0x7c, 0x83, 0x09, 0x1a,
  80. 	};
  81. 	ret = decrypt((char *)a);
  82. 	if (ret == 0) {
  83. 		for (i = 0x10; i < 0x80; ++i) printf("%02x ", a[i]);
  84. 		printf("\n", ret);
  85. 	} else {
  86. 		printf("%08x\n", ret);
  87. 	}
  88. 	return 0;
  89. }
  90.  
Success #stdin #stdout 0s 2052KB
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stdin
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stdout
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43 6f 6d 70 72 65 73 73 65 64 42 47 5f 5f 5f 00 00 05 d0 02 18 00 00 00 00 00 00 00 00 00 00 00 52 46 24 00 ed 2b 9f 02 5b 01 00 00 1d dd 01 00 4c f0 27 e2 3f 77 22 3d 7f a3 41 fd dd ac c1 66 ce 43 74 a4 01 ce 15 91 4e 20 d5 a3 7c 83 09 1a 01 00 00 00 a4 2c c1 bf 10 2c c1 bf 00 a0 71 b7 00 00 00 00 00 00 00 00 00 00 00 00 23 57 5c b7
https://ideone.com/vYiMs9
language:
C (gcc 8.3)
created:
9 years ago
visibility:
public

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