# BOLT Authors - BOLT 03 - Transactions (Highlights) ![rw-book-cover|256](https://opengraph.githubassets.com/cf1f0e0ed825d78ab4fdea8e1da0166563497406a1739429fe9eee36e1b1251d/lightning/bolts) ## Metadata **Review**:: [readwise.io](https://readwise.io/bookreview/38417514) **Source**:: #from/readwise #from/reader **Zettel**:: #zettel/fleeting **Status**:: #x **Authors**:: [[BOLT Authors]] **Full Title**:: BOLT 03 - Transactions **Category**:: #articles #readwise/articles **Category Icon**:: 📰 **URL**:: [github.com](https://github.com/lightning/bolts/blob/master/03-transactions.md#key-derivation) **Host**:: [[github.com]] **Highlighted**:: [[2024-03-06]] **Created**:: [[2024-03-06]] ## Highlights ### Keys #### Key Derivation - The reason for key change is so that trustless watching for revoked transactions can be outsourced. ([View Highlight](https://read.readwise.io/read/01hr9ft4k7ccvq5kbzm5h4nb1g)) ^688808705 ##### `revocationpubkey` Derivation - revocationpubkey = revocation_basepoint * SHA256(revocation_basepoint || per_commitment_point) + per_commitment_point * SHA256(per_commitment_point || revocation_basepoint) ([View Highlight](https://read.readwise.io/read/01hr9fzxsqwa1e05dbm2nqbjj9)) ^688809138 - revocationprivkey = revocation_basepoint_secret * SHA256(revocation_basepoint || per_commitment_point) + per_commitment_secret * SHA256(per_commitment_point || revocation_basepoint) ([View Highlight](https://read.readwise.io/read/01hr9g014z8gza8s2dw0kzha9p)) ^688809150 <!-- New highlights added March 16, 2024 at 11:37 AM --> - This obscures the number of commitments made on the channel in the case of unilateral close, yet still provides a useful index for both nodes (who know the `payment_basepoint`s) to quickly find a revoked commitment transaction. ([View Highlight](https://read.readwise.io/read/01hrxyae48swd3rcp9vf74hkc4)) ^692610579 - amount: the HTLC `amount_msat` divided by 1000 (rounding down) minus fees in satoshis ([View Highlight](https://read.readwise.io/read/01hry264pv3maxnxznaw1pcyrd)) ^692621053 Peers have to maintain the state of balance allocations in msat, otherwise they may create invalid commit transaction because of accumulated errors. Keywords: msat millisatoshis