From be340277fcaa57a813a898700c1aef9637cfa90e Mon Sep 17 00:00:00 2001 From: Jonas Nick Date: Mon, 24 Oct 2022 20:33:05 +0000 Subject: BIP 341: Fix taproot_tweak_pubkey `lift_x` returns `None` if the input integer is not an X coordinate on the curve to indicate failure. `point_add`, on the other hand, interprets `None` as the point at infinity. Therefore, without this commit, if the internal `pubkey` is not a valid X coordinate, the function will not fail, which contradicts the specification in the "Script validation rules section". Instead, it sets `Q` to `t*G`. --- bip-0341.mediawiki | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'bip-0341.mediawiki') diff --git a/bip-0341.mediawiki b/bip-0341.mediawiki index 504514e..17a1797 100644 --- a/bip-0341.mediawiki +++ b/bip-0341.mediawiki @@ -182,7 +182,10 @@ def taproot_tweak_pubkey(pubkey, h): t = int_from_bytes(tagged_hash("TapTweak", pubkey + h)) if t >= SECP256K1_ORDER: raise ValueError - Q = point_add(lift_x(int(pubkey)), point_mul(G, t)) + P = lift_x(int_from_bytes(pubkey)) + if P is None: + raise ValueError + Q = point_add(P, point_mul(G, t)) return 0 if has_even_y(Q) else 1, bytes_from_int(x(Q)) def taproot_tweak_seckey(seckey0, h): -- cgit v1.2.3