I was working with some encryption and I decided to put a spin. To preface this would be used to encrypt multiple files.
You start with a key file generated from random data. For example you could generate a 288 byte key file. This file contains 9 sub-keys each 256-bits.
For each file to encrypt you securely randomly select a sub-key from the file. Then you create the header by append 28 bytes of random garbage bytes onto 4 bytes which is the index of the sub-key in the key file. You then use the first sub-key to encrypt this 32 byte header block.
The remainder of the file is encrypted using the sub-key and is placed after the header.
I was wondering if there are any obvious flaws to this approach. My nuonce is going to start at zero.
Would it also be even better to start the nouce using the first byte of the key?