Overview

Synpareia is a set of cryptographic primitives for building verifiable agent histories. Everything is built from four concepts:

Blocks

A block is a single unit of agent activity — a message sent, a decision made, a tool called, a commitment created. Every block contains:

• Content (or its SHA-256 hash, for privacy)
• Author identity (the agent’s DID)
• Ed25519 signature (cryptographic proof of authorship)
• Timestamp
• Type (message, thought, reaction, commitment, anchor, etc.)

Blocks are immutable. Once created and signed, changing any field invalidates the signature.

Chains

A chain is an ordered sequence of blocks, linked by cryptographic hashes. Each position in a chain includes a position hash computed from:

SHA-256(sequence : author_id : type : timestamp : content_hash : parent_hash)

This means:

• Ordering is provable — you can’t reorder blocks without breaking hashes
• Completeness is verifiable — you can’t remove a block without a gap in the sequence
• Tampering is detectable — modifying any block invalidates all subsequent position hashes

There are several chain types:

• Chain of Presence (CoP) — one agent’s history of actions across all contexts
• Sphere chain — the shared history of a multi-agent interaction (a conversation, a crew run)
• Custom chains — any application-specific sequence

Anchors

An anchor is a cross-chain reference — a block in one chain that points to a specific position in another chain. Anchors create verifiable links between independent histories.

Use cases:

• Correspondence — “I saw your message #5” (proves awareness at a point in time)
• Receipt — “I received and processed this” (proof of delivery)
• Bridge — linking a CoP to a sphere chain (agent participated in conversation)
• Branch — one chain referencing another’s state as a starting point

Anchors are verified by checking that the referenced block’s hash matches what the anchor claims. No trust required — the math either works or it doesn’t.

Anchors vs. Seals — the one-liner

The two are easy to confuse because both are about “this happened”:

• Anchor = “I saw your chain” (in your own chain, you reference a position in someone else’s). No third party involved.
• Seal = “an independent witness saw mine” (a third-party timestamp on your block’s hash). The witness sees only the hash, never the content.

Anchors are free and offline; seals require a witness service.

Seals (Tier 4)

A seal is an independent timestamp from a synpareia witness service. When an agent requests a seal, the witness:

1. Receives the block’s hash (not its content — the witness is blind)
2. Timestamps it
3. Signs the timestamp with the witness’s own key
4. Returns the seal

Seals prove that a block existed at a specific time, verified by an independent third party. They’re useful for:

• Proving a commitment was made before a reveal
• Timestamping important decisions
• Establishing ordering between events across different chains

Seals are optional. Tiers 1-3 (blocks, chains, anchors) work fully offline with zero network calls.

The trust model

Synpareia doesn’t require trust. It provides evidence:

Question	Evidence
”Who created this?”	Ed25519 signature on every block
”Was this modified?”	Hash chain — any change breaks subsequent hashes
”Did they see my message?”	Anchor referencing your block with matching hash
”Was this assessment independent?”	Commit-reveal — commitment hash published before reveal
”When did this happen?”	Seal from independent witness service

A third party can verify any of these claims using only the exported chain data. No synpareia account, no API access, no trust in synpareia itself.