On 2/22/11 at 3:39 PM, [email protected] (Brendan Eich) wrote:
The "API issue" as Erik put it is this: do we need an array of
bytes/shorts/ints, potentially a lot of random values; or would
the fractional bits of a single IEEE 64-bit double precision
result be "good enough".
When doing crypto, mostly what you want is bit banging. For
example, if you are implementing theRC4/ARC4 key schedule (From:
<http://en.wikipedia.org/wiki/Rc4>) you are coding:
for i from 0 to 255
S[i] := i
endfor
j := 0
for i from 0 to 255
j := (j + S[i] + key[i mod keylength]) mod 256
swap values of S[i] and S[j]
endfor
The AES process is similar (from:
<http://en.wikipedia.org/wiki/Advanced_Encryption_Standard>):
High-level description of the algorithm
1. KeyExpansion—round keys are derived from the cipher key
using Rijndael's key schedule
2. Initial Round
1. AddRoundKey—each byte of the state is combined with
the round key using bitwise xor
3. Rounds
1. SubBytes—a non-linear substitution step where
each byte
is replaced with another according to a lookup table.
2. ShiftRows—a transposition step where each row of
the state
is shifted cyclically a certain number of steps.
3. MixColumns—a mixing operation which operates on
the columns
of the state, combining the four bytes in each column.
4. AddRoundKey
4. Final Round (no MixColumns)
1. SubBytes
2. ShiftRows
3. AddRoundKey
I always think of these operations as shifting and masking, but
I'm really an Assembler/OS guy who likes being close to the
hardware. :-)
Other uses will be packaging it into network messages, as in
SSL/TLS key generation.
Are there other, non-crypto uses for secure random numbers?
The question for the Javascript experts is, what form will make
implementing this kind of code easiest?
Cheers - Bill
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