scrypt-1.2.1/FORMAT

   1 scrypt encrypted data format
   2 ----------------------------
   3
   4 offset  length
   5 0       6       "scrypt"
   6 6       1       scrypt data file version number (== 0)
   7 7       1       log2(N) (must be between 1 and 63 inclusive)
   8 8       4       r (big-endian integer; must satisfy r * p < 2^30)
   9 12      4       p (big-endian integer; must satisfy r * p < 2^30)
  10 16      32      salt
  11 48      16      first 16 bytes of SHA256(bytes 0 .. 47)
  12 64      32      HMAC-SHA256(bytes 0 .. 63)
  13 96      X       data xor AES256-CTR key stream generated with nonce == 0
  14 96+X    32      HMAC-SHA256(bytes 0 .. 96 + (X - 1))
  15
  16 AES256-CTR is computed with a 256-bit AES key key_enc, and HMAC-SHA256 is
  17 computed with a 256-bit key key_hmac, where
  18   scrypt(password, salt, N, r, p, 64) == [key_enc][key_hmac]