encrypting a sequence of bytes

Question

i have 5 random bytes. i want to encrypt/transformate these 5 bytes in some way.
i don't want to use any key(like private key), but some formel or transformation(e.g. shifting bytes, change positions, add, divide etc).
what formel could i use or please tell me some search words for google=)

kovan · Answer

multiply each byte by -1?

spgilmore · Answer

I must say right off that this encryption method will not be secure without a key. One thing you can always do is XOR, which is NEVER recommended in encryption, but always seems to get used anyway. You can XOR against any arbitrary number to encrypt, then XOR it against the same number to unencrypt. $FFFFFFFF is a popular choice. It is very chaotic, which is often good in encryption. Another thing you can do is to rotate bits on each byte (not bitshift, as that is lossy). Each byte position is a number that you can use to affect the running algorithm, but to throw things off, you might want to rotate by a modulus of the position number, and and some exceptions, such as when a position number is divisible by 3, rotate it 1 extra time, etc. Another element of chaos could *sometimes* be the length of the input, the checksum or CRC of the input, the average of the input, etc.
Get creative.