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162 lines
4.8 KiB
Markdown
162 lines
4.8 KiB
Markdown
---
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title: Summon Major Update
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image: "/articles/summon-major-update/cover.webp"
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tldr: I’m excited to share the biggest Summon update yet. 🎉
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authors: ["Andrew Morris"]
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date: 2025-05-21
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tags:
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[
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summon,
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mpc,
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typescript,
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privacy,
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developer-tools,
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release-notes,
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circuits,
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cryptography,
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compiler,
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]
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projects: ["mpc-framework"]
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canonical: "https://mpc.pse.dev/blog/summon-major-update"
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---
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I’m excited to share the biggest Summon update yet. 🎉
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## Wait - What's Summon?
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[Summon](https://github.com/privacy-scaling-explorations/summon) is a dialect of TypeScript for generating boolean circuits! We use this to great effect in [MPC Framework](https://mpc.pse.dev/), since it requires the computation inside the MPC cryptography to be a boolean circuit. It's so much more than a TypeScript library - it's a very special runtime that transforms branching (`if/else/for/while/switch`) into flat circuitry.
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## 1 · Streamlined IO with `Summon.IO`
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### Before
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```js
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export default function main(a: number, b: number) {
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const plus = a + b
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const gt = a > b
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return [plus, gt]
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}
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// and separately provide mpcSettings:
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const mpcSettings = [
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{
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name: "alice",
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inputs: ["a"],
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outputs: ["main[0]", "main[1]"],
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},
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{
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name: "bob",
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inputs: ["b"],
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outputs: ["main[0]", "main[1]"],
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},
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]
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```
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### After
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```js
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default function main(io: Summon.IO) {
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const a = io.input('alice', 'a', summon.number());
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const b = io.input('bob', 'b', summon.number());
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io.outputPublic('plus', a + b);
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io.outputPublic('gt', a > b);
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}
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// mpcSettings is generated automatically
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```
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_Shorter, self‑contained, and each output has a real name._
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Per-party outputs are also coming, and will fit neatly into this API: `io.output(partyName, outputName, value)`.
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Type information is available via [`summon.d.ts`](https://github.com/privacy-scaling-explorations/summon/blob/main/summon.d.ts):
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## 2 · Typed Inputs (now with `bool`)
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The third argument of `io.input` specifies the type:
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`bool`s now work properly, so you can pass `true`/`false` instead of `1`/`0`. This is both better devX and removes unnecessary bits.
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Output bools are also new, decoding correctly as `true`/`false` (the values you get out of `await session.output()`).
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This also sets us up to support arrays/etc and grow into comprehensive typing à la [zod](https://zod.dev/?id=basic-usage) or [io‑ts](https://github.com/gcanti/io-ts/blob/master/index.md).
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## 3 · Public Inputs
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Need a single program that adapts to many input sizes/participants? Public inputs let you accept these at **compile time**:
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```js
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const N = io.inputPublic("N", summon.number())
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let votes: boolean[] = []
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for (let i = 0; i < N; i++) {
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const vote = io.input(`party${i}`, `vote${i}`, summon.bool())
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votes.push(vote)
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}
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```
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Pass them via CLI:
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```bash
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summonc program.ts \
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--public-inputs '{ "N": 10 }' \
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--boolify-width 8
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```
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or the `summon-ts` API:
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```js
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const { circuit } = summon.compile({
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path: "program.ts",
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boolifyWidth: 8,
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publicInputs: { N: 10 },
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files: {
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/* ... */
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},
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})
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```
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See it in action: **JumboSwap** [circuit](https://github.com/privacy-scaling-explorations/jumboswap/blob/3f81b87/src/circuit/main.ts).
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## 4 · Faster Branch Merging
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Merging has to occur whenever your program branches on signals:
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```js
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const value = cond ? x : y
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```
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Circuits can't evaluate only one side of this like CPUs do, so the Summon compiler has to emit wires for both branches and then merge them together like this:
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```js
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value = merge(condA, x, condB, y)
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// = (condA * x) + (condB * y) // old method
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// = (condA * x) XOR (condB * y) // new method
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```
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So, `+` became `XOR` which is great because `XOR` is almost free, but why is this allowed?
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The key is that `condA` and `condB` cannot be true simultaneously. In this example we have `condB == !condA`, but we don't have to rely on that. These conditions are _always_ non-overlapping - there is only ever one "real" branch with `cond == 1`. This means each bit of the addition cannot produce a carry and is equivalent to `XOR`, because `XOR` is 1-bit addition.
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This caused some real speedups in our demos:
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- [**JumboSwap**](https://mpc.pse.dev/apps/jumboswap): ≈4× faster
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- [**Lizard‑Spock**](https://mpc.pse.dev/apps/lizard-spock): ≈20 % faster
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## Join Us!
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- [Telegram group](https://t.me/+FKnOHTkvmX02ODVl)
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- [Discord](https://discord.gg/btXAmwzYJS) (Channel name: 🔮-mpc-framework)
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- [Github Repo](https://github.com/privacy-scaling-explorations/mpc-framework) ⭐️
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- [Website](https://mpc.pse.dev)
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Thanks for building privacy‑preserving magic with us! 🪄
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