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0 pointspbsd11y ago0 comments

The way your scalar multiplication is performed leaves you open to two attacks:

- Scalar multiplication is variable-time, with the variation being correlated with the position of the most significant bit of the exponent (see https://github.com/Bren2010/ecc/blob/bd75261b6fe7839ddc751d6...). An attack like [1] on ECDSA seems plausible.

- The Montgomery ladder uses different code paths depending on whether the exponent bit is 0 or 1; this makes FLUSH+RELOAD attacks possible, as in [2].

[1] https://eprint.iacr.org/2011/232

[2] https://eprint.iacr.org/2014/140

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bren201311y ago

Issue #1: Yes, it's supposed to be like that. The point is that any n-bit scalar takes the same amount of time as any other n-bit scalar.

Issue #2: Rust has explicitly taken all memory management away from me. There's nothing I can do about that.

j / k navigate · click thread line to collapse

0 comments

bren201311y ago

Issue #1: Yes, it's supposed to be like that. The point is that any n-bit scalar takes the same amount of time as any other n-bit scalar.

Issue #2: Rust has explicitly taken all memory management away from me. There's nothing I can do about that.

j / k navigate · click thread line to collapse