Remedy Archive System

Revision as of 16:47, 21 November 2025

Remedy Archive System is used to store game data for Remedy Entertainment games such as Max Payne and Max Payne 2. The metadata (central directory) following the header is encrypted.

Identification

Files begin with signature bytes 52 41 53 00.

Format details

Numbers are in little-endian byte order.

The file's header has the following structure:

struct RASHeader {
  uint8_t magic[4]; // "RAS\0"
  uint32_t encryptionKey;
};

The next section of the header must be decrypted first:

// decrypted structure
struct RASMetadata {
  uint32_t unknown0;
  uint32_t unknown1;
  uint32_t centralDirectoryLength;
  uint32_t unknown3;
  float32_t version; /* binary32 according to IEEE 754 */
  uint32_t unknown5;
  uint32_t unknown6;
  uint32_t unknown7;
  uint32_t compatibility;
};

Encryption

Depending on the generation of the RAS file format, different encryption schemes are used.

RAS1 (Max Payne)

void decrypt(uint8_t *buf, size_t count, int32_t key) {
  size_t i;
  uint8_t a;
  uint8_t b;

  if (key == 0) {
    key = 1;
  }
  for (i = 0; i < count; i++) {
    uint8_t a = buf[i];
    uint8_t b = ((uint8_t)(i % 5)) & 7;
    buf[i] = rotateLeftByte(a, b);
    key = key * 171 + (key / 177) * -30269;
    buf[i] = (((((uint8_t)i) + 3) * 6) ^ buf[i]) + ((uint8_t)key);
  }
}

If your programming language doesn't support the rotateLeftByte operation, it can be emulated using:

uint8_t rotateLeftByte(uint8_t a, uint8_t b) {
  return (a << b) | (a >> (8 - b));
}