WIP: Add aggsig example code #505
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jonasnick
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examples/aggsig.c
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| return 1; | ||
| } | ||
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| /* Sign a message hash with the given key pairs and and store the result in sig */ |
examples/aggsig.c
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| /* Verify an aggregated signature of n_pubkeys pubkeys over msghash */ | ||
| int verify(const secp256k1_context* ctx, const unsigned char *sig, const unsigned char *msghash, const secp256k1_pubkey *pubkeys, size_t n_pubkeys) { |
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You use N_PUBKEYS in other functions but here you add a size_t n_pubkeys. Particular reason or just ended up that way? (You only call this with N_PUBKEYS as argument I think.)
examples/aggsig.c
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| scratch_size = 9000; | ||
| } | ||
| scratch = secp256k1_scratch_space_create(ctx, 0, scratch_size); | ||
| if(scratch == NULL) { |
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Nit: You're mixing if() and if () style, and the same for for() and for (). Personally prefer the latter, but probably shouldn't mix.
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good catch, thanks!
| int i; | ||
| unsigned char seckeys[N_PUBKEYS][32]; | ||
| secp256k1_pubkey pubkeys[N_PUBKEYS]; | ||
| unsigned char msghash[32] = "this_should_actually_be_msg_hash"; |
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This will actually overbuffer, writing a \0 into the 33rd byte of msghash. Surprised compilers don't warn about that.
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Hm, http://port70.net/~nsz/c/c89/c89-draft.html#3.5.6 says terminating null characters are only added "if there is room".
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That would explain the lack of compiler warnings! First thing I ever heard of such an arbitrary rule. C can be freaky.
jonasnick
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Closing as this will be probably superseded by MuSig |
Based on #461 + some things I suggested for that PR.
I think it'd be a good idea to have some example code to show how to use the aggsig module. For example, the seed of the nonce RNG could be misused and it's not all that intuitive how a scratch space is used. This PR addresses this by adding an
aggsig.cfile into anexamples/directory and building it asexample_aggsig(it's also run as part ofmake check).Since #461 does not allow for multi party signing at the moment,
aggsig.cdemonstrates single user signing and verification for now.