Re: [bug-gnulib] arcfour

[Bruno Haible]

Simon Josefsson wrote:

> +/* Initialize CONTEXT using encryption KEY of KEYLEN bytes.  KEY
> +   should be 40 bits (5 bytes) or longer.  */
> +extern void
> +arcfour_setkey (arcfour_context * context, const char *key, size_t keylen);

The comment should say that KEYLEN must be > 0. (If keylen==0, your
first code would do divisions by 0, and Ralf's replacement code would do
out-of-bounds array accesses.)

> +arcfour_stream (arcfour_context * context, const char *inbuf, char *outbuf, 
> size_t length)
> +{
> +  register size_t i = context->idx_i;
> +  register size_t j = context->idx_j;
> +  register unsigned char *sbox = context->sbox;
> +  register unsigned char t;

Usually I try to minimize the scope of variables, i.e. I would declare
'unsigned char t;' at the beginning of the loop. Like you are doing in
arcfour_setkey.

> +  while (length--)

If you write this as

     for (; length > 0; length--)

the CPU has one instruction less to execute per function call.

Bruno