What a Signature Can See · 签名能看见什么 · the SIGHASH playground

Here is a whole Bitcoin transaction, laid out field by field (Sparrow-style). A signature does not cover all of it. Your sighash flag decides which fields the signature SEES (看) — commits to — and which it leaves BLIND (蒙). Blind fields can be changed by anyone after you sign. Flip the dials and watch the transaction grey out. The 32-byte digest on the right is the real message your key signs.

Example

OUTPUT dial

INPUT dial

ANYONECANPAY

flag
SIGHASH_ALL 0x01

SEE 看 = committed (change it → signature dies) · = not committed (anyone can change it)

The transaction — colored & annotated, with your flag applied

Hit ✎ tamper on any field to see what happens if someone changes it after you sign, under the current flag.

where you are on the 2×3 matrix

→ folded into the message you sign

The SEE fields on the left are hashed into these commitments. BLIND groups simply aren't here.

TapSighash digest — what your key actually signs:

…

after you sign — locked vs open

Real BIP-341 computed in your browser (self-contained SHA-256, no network). Byte-verified against bitcoinutils in print_sighash_fields.py (18/18 digests match). Companion to the book What a Signature Can See.