A very old idea
Nothing in Souspli is new except the cryptography. Every property it offers was once ordinary, and most of them have a name. This page collects the precedents, because "how people did this for centuries" is a better explanation than any diagram.
The name
Sous pli is French for "under cover": a document sent sous pli cacheté travels folded and sealed, for its addressee only. The unit of Souspli is a letter, and the wire format had the vocabulary before the project had a name — letters have envelopes, may be sealed, and carry enclosures.
Open letters and closed ones
Medieval chanceries issued two kinds of letter. Letters patent (litterae patentes, "open letters") were addressed to everyone, with the seal hanging from the bottom so the text could be read without breaking it. Letters close (litterae clausae) were folded and sealed shut, for the recipient alone.
Souspli draws exactly that line: a public letter anyone may read and verify, and a sealed letter only its recipients can open — including the fact of who wrote it.
What is written stays
Vox audita perit, littera scripta manet — the heard voice perishes, the written letter remains.
A web page is a voice: it says something to you, once, and nothing is left. The point of writing was always that both parties could go back to it.
Ne varietur ("so that nothing be changed") is what is written on a document when it is marked page by page so that no sheet can later be swapped. A content hash is the same act, done by arithmetic: change one byte and it is a different document.
Each party keeps a copy
A chirograph was a contract written out twice on one sheet, then cut apart through a word written across the middle — often along a wavy, indented line, whence "indenture". Each party kept a half; bringing the halves together proved both were genuine. Contracts are still "executed in counterparts": every signatory holds an original.
That is Souspli's answer to "where is the system of record?" — in each party's hands. A co-signed contract is one document with several independent signatures over the same bytes, and everyone who signed holds all of it.
French law has a category for a document the parties sign themselves, with no public officer involved: the acte sous seing privé. No notary, no registry, no platform — and fully valid. Most of what people do with each other has always worked that way.
The letter is its own envelope
Before gummed envelopes, people folded, slit, tucked and sealed a letter so that it became its own tamper-evident packet — a practice conservators now call letterlocking. Opening it left marks. No third party was involved in its security; the security was a property of the object.
A Souspli bundle is the same kind of object: the proof of who wrote it, and that it has not been altered, travels inside it and can be checked by anyone holding it, offline, without asking anybody.
Organising by letter
- The Republic of Letters was the community of scholars who, across the 17th and 18th centuries, ran European science and philosophy through correspondence — letters copied, forwarded, read aloud and answered, across borders and wars.
- The American colonies' committees of correspondence organised a revolution by post.
- Samizdat — "self-published" — was literature retyped and handed on, reader to reader, because there was no permitted channel. Each reader was also a publisher.
- In Japanese neighbourhoods a kairanban (回覧板, "circulating board") still goes door to door: each household reads the notice, stamps it with its seal, and passes it to the next. A signed, circulating document, organising a community.
- In Scandinavia a budstikke — a bidding stick — was relayed farm to farm to summon people to the assembly, and the law obliged you to pass it on.
That assembly was the ting. It is the same word as English "thing", which
meant a meeting before it meant a matter discussed at one, and only later an object.
Inside Souspli's code a letter is still called a thing — named, by accident, after
the oldest word there is for free people meeting to decide something.