refactor: split up internal pubkey serialization function into compressed/uncompressed variants #1774
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w0xlt
approved these changes
Nov 18, 2025
furszy
reviewed
Nov 18, 2025
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furszy
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furszy
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Looks good, just left a minor nit. No need to tackle it.
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292
| if (secp256k1_pubkey_load(ctx, &Q, pubkey)) { | ||
| ret = secp256k1_eckey_pubkey_serialize(&Q, output, &len, !!(flags & SECP256K1_FLAGS_BIT_COMPRESSION)); | ||
| if (ret) { | ||
| *outputlen = len; | ||
| if (flags & SECP256K1_FLAGS_BIT_COMPRESSION) { | ||
| secp256k1_eckey_pubkey_serialize33(&Q, output); | ||
| *outputlen = 33; | ||
| } else { | ||
| secp256k1_eckey_pubkey_serialize65(&Q, output); | ||
| *outputlen = 65; | ||
| } | ||
| ret = 1; | ||
| } | ||
| return ret; |
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In adb76f8:
nit: could remove ret if you write it as:
if (!secp256k1_pubkey_load(ctx, &Q, pubkey)) return 0;
if (flags & SECP256K1_FLAGS_BIT_COMPRESSION) {
secp256k1_eckey_pubkey_serialize33(&Q, output);
*outputlen = 33;
} else {
secp256k1_eckey_pubkey_serialize65(&Q, output);
*outputlen = 65;
}
return 1;
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Makes sense yeah, will do if I have to retouch
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This PR splits up the pubkey serialization function
secp256k1_eckey_pubkey_serializeinto two variants for the compressed (33 bytes) and uncompressed (65 bytes) public key output format each, where only non-infinity group elements as input are allowed. The motivation is to simplify call-sites significantly, as they currently need to introduce two variables and a VERIFY_CHECKs on the return value and the in/out size parameter within a pre-processor block, typically leading to 8 lines of code. By using the new functions, the code is reduced to a single line of code that just calls the function (see #1773). This is helpful for already existing modules on master (ellswift, musig) and upcoming ones (silentpayments, see #1765).One drawback is that the public API function
secp256k1_ec_pubkey_serializeis now slightly more complex (we now call one of two functions instead of a single one, depending on whether the compressed flag is set or not), but that should hopefully not be a problem.The commits are intentionally kept small to ease review, happy to squash them if that is preferred.
(Kudos to w0xlt for the initial idea (#1765 (review)) and to real-or-random for the suggestion to split the already existing function (#1773 (comment)).)