Remedy Archive System

File Format
Name	Remedy Archive System
Ontology	Electronic File Formats Game data files Remedy Archive System
Extension(s)	.ras
Released	2001

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 {
  
};

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));
}