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Correct htlc witness size calculations (#815)

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* BOLT#3: use 4 bytes for cltv_expiry in accepted_htlc_script
* BOLT#3: correct success_witness size
* BOLT#3: note HTLC tx weights differ a bit from actual weights
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Johan T. Halseth 2020-12-07 21:32:29 +01:00 committed by GitHub
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03-transactions.md
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@ -829,7 +829,7 @@ Multiplying non-witness data by 4 results in a weight of:
The *expected weight* of an HTLC transaction is calculated as follows:
accepted_htlc_script: 139 bytes (142 bytes with option_anchor_outputs)
accepted_htlc_script: 140 bytes (143 bytes with option_anchor_outputs)
- OP_DUP: 1 byte
- OP_HASH160: 1 byte
- OP_DATA: 1 byte (RIPEMD160(SHA256(revocationpubkey)) length)
@ -859,7 +859,7 @@ The *expected weight* of an HTLC transaction is calculated as follows:
- OP_ELSE: 1 byte
- OP_DROP: 1 byte
- OP_DATA: 1 byte (cltv_expiry length)
- cltv_expiry: 3 bytes
- cltv_expiry: 4 bytes
- OP_CHECKLOCKTIMEVERIFY: 1 byte
- OP_DROP: 1 byte
- OP_CHECKSIG: 1 byte
@ -916,7 +916,7 @@ The *expected weight* of an HTLC transaction is calculated as follows:
- witness_script_length: 1 byte
- witness_script (offered_htlc_script)
success_witness: 325 bytes (328 bytes with option_anchor_outputs)
success_witness: 324 bytes (327 bytes with option_anchor_outputs)
- number_of_witness_elements: 1 byte
- nil_length: 1 byte
- sig_alice_length: 1 byte
@ -954,11 +954,12 @@ The *expected weight* of an HTLC transaction is calculated as follows:
- lock_time: 4 bytes
Multiplying non-witness data by 4 results in a weight of 376. Adding
the witness data for each case (285 or 288 + 2 for HTLC-timeout, 325 or 328 + 2 for
the witness data for each case (285 or 288 + 2 for HTLC-timeout, 324 or 327 + 2 for
HTLC-success) results in weights of:
663 (HTLC-timeout) (666 with with option_anchor_outputs))
703 (HTLC-success) (706 with with option_anchor_outputs))
663 (HTLC-timeout) (666 with option_anchor_outputs))
703 (HTLC-success) (706 with option_anchor_outputs))
- (really 702 and 705, but we use these numbers for historical reasons)
# Appendix B: Funding Transaction Test Vectors