Mixes fresh entropy into the generator (SP 800-90A's Reseed function) and resets its request count. Use it after many requests (the standard requires a reseed after \(2^{48}\)), to add prediction resistance before a sensitive draw, or to replay a known-answer test that reseeds with given entropy.
Arguments
- drbg
A generator from
drbg_new().- entropy
Entropy input: exactly 48 bytes, raw or hex;
NULL(the default) draws them from the operating system's CSPRNG.- additional
Optional additional input of up to 48 bytes, raw or hex; default
NULL(none).
Details
The new (Key, V) is derived from the old state, the 48 entropy bytes and the
additional input, so the stream after the reseed depends on everything that
went before. The request count is reset to 1 and the generator is marked as
belonging to the current process. Errors: drbg not made by
drbg_new(); entropy not exactly 48 bytes;
additional longer
than 48 bytes; either not raw or hex.
Examples
d <- drbg_new(as.raw(0:47))
drbg_reseed(d, as.raw(48:95))
drbg_generate(d, 8)
#> [1] 7b 58 11 e6 34 ba 47 e2
# a reseed with given entropy is reproducible
d2 <- drbg_new(as.raw(0:47))
drbg_reseed(d2, as.raw(48:95))
identical(drbg_generate(d2, 8),
drbg_generate(drbg_reseed(drbg_new(as.raw(0:47)), as.raw(48:95)), 8))
#> [1] TRUE
# fresh entropy from the operating system, with additional input
drbg_reseed(d, additional = charToRaw("before key generation"))
# the entropy must be exactly 48 bytes
try(drbg_reseed(d, as.raw(1:10)))
#> Error : `entropy` must be exactly 48 bytes, raw or hex