Verify Signatures are in the correct Sub-group

ethereum / py_ecc

Python implementation of ECC pairing and bn_128 and bls12_381 curve operations

MIT License

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Verify Signatures are in the correct Sub-group #80

Open kirk-baird opened 4 years ago

kirk-baird commented 4 years ago

py-ecc Version: 1.7.1

What is wrong?

Currently verification of a signature does not check that the signature is in the correct subgroup. This poses a security risk when verifying a pairing.

How can it be fixed

When verifying a signature check r * sig == 0 before pairing.

I will update #79 to include the check as this had been inserted into the standard.

pipermerriam commented 4 years ago

If this isn't explicitely part of #79 maybe this change can be extracted to a stand-alone PR?

kirk-baird commented 4 years ago

I made this PR cause it is a security vulnerability that currently exists but it is included as part or the BLS stand.

Do you this it should be it's own PR or part of the BLS standard PR?

kirk-baird commented 4 years ago

I've added this in #79