- let writeByteToCipherFileAt byte position =
- using (new FileStream (cipherFilename, FileMode.Open, FileAccess.Write))
- (fun fs -> fs.Position <- position
- fs.Write ([| byte |], 0, 1))
+ let incrementByteCipherFileAt position =
+ use fs = new FileStream (cipherFilename, FileMode.Open, FileAccess.ReadWrite)
+ fs.Position <- position
+ let byte = fs.ReadByte () |> byte
+ fs.Position <- position
+ fs.Write ([| byte + 1uy |], 0, 1) // Modulo 256.