The seedfile needs to have the size of the entropy accumulator, which
is 64 bytes (512 bits) since the entropy accumulator uses SHA-512 and
the seed size needs to be the same as the hash output (or larger).
We used to enable MBEDTLS_ENTROPY_FORCE_SHA256 in the full config, so
the entropy accumulator was 256 bits (32 bytes), and therefore a
32-byte seedfile worked. But we no longer turn on this option in the
full config, so the 32-byte seedfile no longer works.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
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