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Fix an overflow bug in rsaz_512_sqr
There is an overflow bug in the x64_64 Montgomery squaring procedure used in
exponentiation with 512-bit moduli. No EC algorithms are affected. Analysis
suggests that attacks against 2-prime RSA1024, 3-prime RSA1536, and DSA1024 as a
result of this defect would be very difficult to perform and are not believed
likely. Attacks against DH512 are considered just feasible. However, for an
attack the target would have to re-use the DH512 private key, which is not
recommended anyway. Also applications directly using the low level API
BN_mod_exp may be affected if they use BN_FLG_CONSTTIME.


Reviewed-by: Paul Dale <>
Reviewed-by: Bernd Edlinger <>
(Merged from #10576)
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dot-asm authored and bernd-edlinger committed Dec 4, 2019
1 parent b39c047 commit f1c5eea8a817075d31e43f5876993c6710238c98
Showing with 206 additions and 193 deletions.
  1. +206 −193 crypto/bn/asm/

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