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

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)

function decrypt(data: byte[], key: uint32):
  if key == 0:
    key := 1
 
  for i from 0 to data.length-1:
    a := data[i]
    b := i mod 5         -- such that 0 ≤ b < 5
    c := rotateByteLeft(a by b)
    d := key / 177
    e := d * 30269
    f := key * 171
    key := f - e
    g := i mod 256
    h := g + 3
    k := h * 6
    m := k bitwiseXor data[i]
    p := key mod 256     -- such that 0 ≤ p < 256
    q := m + p
    data[i] := q mod 256

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

function rotateByteLeft(i by n):
  return (i bitShiftLeft n) bitwiseOr (i bitShiftRight (8 - n))