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trezor / python-shamir-mnemonic

MIT License
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Why is the code not shared with trezor firmware? #23

Closed infokiller closed 4 years ago

infokiller commented 4 years ago

Hey,

Looking at trezor-firmware, I see a parallel implementation. I assume some of the code can't be shared because of the different computing environments assumed, but it seems there's currently no code sharing at all. Why is that?

Thanks

andrewkozlik commented 4 years ago

The implementation in python-shamir-mnemonic is intended for reference purposes and, for example, to generate test vectors. The trezor-firmware version is aimed at a more secure, albeit less legible implementation. One important example of this is the interpolate function which uses a table of discrete logarithms in the reference implementation, https://github.com/trezor/python-shamir-mnemonic/blob/master/shamir_mnemonic/__init__.py#L132. In comparison trezor-firmware uses a C implementation of this function, https://github.com/trezor/trezor-firmware/blob/master/crypto/shamir.c, which is more resilient against side channel leakage.

I am sure some of the functions from the reference implementation could be reused in trezor-firmware, but I am not sure it's worth the trouble. Perhaps something to consider as part of https://github.com/trezor/trezor-firmware/issues/407.

infokiller commented 4 years ago

Thanks for the quick response! Other than the lack of memory obfuscation/protection and side channel leakage, are you aware of any other vulnerabilities in the reference implementation (related to #17)?

andrewkozlik commented 4 years ago

Other than the lack of memory obfuscation/protection and side channel leakage, are you aware of any other vulnerabilities in the reference implementation (related to #17)?

I don't recall anything else.