Topics: Add Swap-in Potentiam (SIP)

_topics/en/swap-in-potentiam.md

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+---
+title: Swap-in Potentiam (SIP)
+
+## Optional. test Shorter name to use for reference style links e.g., "foo"
+## will allow using the link [topic foo][].  Not case sensitive
+shortname: swap-in potentiam
+
+## Optional.  An entry will be added to the topics index for each alias
+#aliases:
+#  - Foo
+
+## Required.  At least one category to which this topic belongs.  See
+## schema for options
+topic-categories:
+  - Contract Protocols
+  - Lightning Network
+
+## Required.  Use Markdown formatting.  Only one paragraph.  No links allowed.
+## Should be less than 500 characters
+excerpt: >
+  **Swap-in-Potentiam (SIP)** is a protocol that facilitates the immediate transfer of confirmed
+  on-chain Bitcoin to the Lightning Network. It reduces trust requirements compared to other
+  instant channel opening methods like 0-conf channels by temporarily committing to co-ownership with a Lightning Service
+  Provider (LSP) and delaying unilateral access per a timeout.
+
+## Optional.  Produces a Markdown link with either "[title][]" or
+## "[title](link)"
+primary_sources:
+  - title: Moving Onchain Funds "Instantly" To Lightning (Jesse Posner, ZmnSCPxj)
+    link: https://lists.linuxfoundation.org/pipermail/lightning-dev/2023-January/003810.html
+
+  - title: LSPS C= Extension, Swap-in-Potentiam
+    link: https://github.com/ZmnSCPxj-jr/swap-in-potentiam/blob/master/doc/swap-in-potentiam.md
+
+## Optional.  Each entry requires "title", "url", and "date".  May also use "feature:
+## true" to bold entry
+optech_mentions:
+  - title: "Swap-in Potentiam Announced"
+    url: /en/newsletters/2023/12/20/#swap-in-potentiam
+
+  - title: Non-interactive LN channel open commitments
+    url: /en/newsletters/2023/01/11/#non-interactive-ln-channel-open-commitments
+
+## Optional.  Same format as "primary_sources" above
+see_also:
+  - title: Hash Time Locked Contracts from Bitcoin Wiki
+    link: https://en.bitcoin.it/wiki/Hash_Time_Locked_Contracts
+
+  - title: Swap-in potentiam for Phoenix
+    link: https://gist.github.com/t-bast/5fd89979a8088b99d0b95c124902aa56
+  - title: Swaproot
+    link: https://acinq.co/blog/phoenix-swaproot
+
+  - title: Payjoin-in-Potentiam
+    link: https://delvingbitcoin.org/t/payjoin-in-potentiam-externally-fund-an-lsp-channel-open-with-one-transaction/749
+
+---
+Swap-in potentiam (SIP) differs from typical HTLC-based swaps by
+allowing for a pre-commital stage. This allows for; reusable swap addresses,
+immediate transfers to lightning, and reduced trust requirements compared to
+0-conf channels.
+
+In this scheme, the reusable swap address is a contract between Alice and Bob
+that allows for two spend paths; Alice and Bob cosign, or Alice
+can spend unilaterally after a timeout.
+
+Once the swap address is funded and confirmed, Alice can choose one of the
+following options; swap the funds into a new or existing lightning network
+channel with the help of Bob, or send the funds to a new onchain address with
+the help of Bob. Alice also has the third option of waiting for the recovery
+timeout if Bob is offline or uncooperative.
+
+SIP is primarily geared towards mobile users who may go offline for extended
+periods, and a variation called swaproot has been implemented in Phoenix wallet.
+
+{% include references.md %}