re how large are commercial keys in apr ee eng ohio state edu butzerd maumee eng ohio state edu dane c butzer writes what are the typical sizes for keys for commercial secret key algorithms i know des is bits tripple des is bits and idea is bits is there anything made in the us that has bit keys anything anywhere that has larger keys i ve heard that rc can be scaled to arbitrarily large keys but is this actually implemented anywhere my mdc cipher which uses any one way hash function as a cfb mode stream cipher the current implementation uses md uses a key of up to bits that is you can use a bit key if you want and copy it over the entire bit range or you can use the entire bits runtime is independant of key size the system runs slightly slower than md itself i presume rc and rc use a similar system or possibly they just hash an arbitrary length key down to n bits maybe using something like md peter
