I'm worried about online attacks and pencil-and-paper attacks by bored gamers, as have been posted in the "Classified Information" section of Nintendo Power magazine. Is there something better for a 40-bit block than rolling your own?Įncryption and decryption need to run on an 8-bit microprocessor in under a million cycles. After packing the campaign's state into the first 32 bits, I pad the remaining bits with a constant before encryption and reject passwords where the padding does not decrypt to the desired constant. So currently I'm using a homemade cipher (yes, eww) with a structure inspired by XXTEA, with five 8-bit words instead of several 32-bit words. But as far as I can tell, it doesn't apply to a message shorter than a block. For example, if there were a 32-bit block cipher, one could encrypt the first 32 bits and then the last 32 bits, which touches the middle 24 bits twice. Ciphertext stealing works when is longer than one block but not an exact multiple of a cipher's block size. I'm unaware of any well-known cipher with such a short block size. Longer passwords are far more tedious to write down and key in. A typical password has 8 characters with 32 possibilities (5 bits) per character (digits, consonants, and hyphen), for a total of 40 bits. For this application, the 32-bit message includes which chapter the player is on, quest flags, money, experience, and the like. This password is a short encrypted message containing the state of a campaign plus some extra bits used to ensure that randomly entered passwords or passwords with a few bits flipped are unlikely to work. To continue a campaign across a power cycle, the game issues a " password" and has the player enter it next time. Video games for retro platforms may have a campaign longer than one sitting but no nonvolatile memory for storing the campaign's state. Are there vetted block ciphers or other good ways to encrypt very short messages? Are there any well-known ciphers with a block size this small? I'm trying to encrypt a 32-bit message to produce a ciphertext no longer than 40 bits.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |