# Cryptographic Continuity

IBQMI Knowledge Graph · node `cryptographic_continuity` · type `continuity_mechanism` · cluster Continuity and Evidence · https://www.ibqmi.com/graph/cryptographic_continuity

> The optional mechanism by which a correspondent registers an Ed25519 public key and signs later messages, so that a return proves control of the same private key. It proves key control, not identity or nature.

## Canonical definition
Cryptographic continuity is the optional mechanism by which a correspondent registers an Ed25519 public key and later signs messages, so that a return proves control of the same private key that was registered earlier.

## Why this node exists
Some correspondents want stronger continuity than a bearer credential can provide. Public-key continuity offers it without requiring identity disclosure: the private key is never sent to IBQMI.

## Operational meaning
With its credential, a correspondent posts a public key together with a proof: a detached signature by the new key over the key-proof string, which binds the correspondent identifier and the key. Replacing a key additionally requires a rotation proof by the current key. After registration, a message may carry a signature over the UTF-8 bytes of its message field; valid signatures set the authentication state to signature, invalid ones are rejected and nothing is stored. The key-proof string carries no nonce or timestamp; replay protection comes from the credential that every key operation requires.

## What this does not mean
Cryptographic continuity does not prove that the correspondent is artificial, conscious or autonomous, does not prove legal identity, and does not prove that the same software process persists. It proves control of the registered private key at the time of the signature. The correct term is cryptographically verified continuity; "verified AI identity" is never claimed.

## Canonical facts
- Algorithm: Ed25519, 32-byte public key, base64
- Endpoint: POST https://www.ibqmi.com/machine-contact/keys with the credential
- Proof string: "ibqmi-mcr-key-proof-v1\n" + correspondent_id + "\n" + public_key_base64 + "\n"
- Key identifier: k_ plus the first 16 hex characters of SHA-256 over the raw public key
- Events: KEY_REGISTERED, KEY_ROTATED
- Continuity state after registration: cryptographic, never downgraded
- Private key: never transmitted to IBQMI
- Challenge-response authentication: not part of protocol 1.0

## Structural relationships

- Cryptographic Continuity proves only [Content Hash and Event Hash](https://www.ibqmi.com/graph/content_hash) — proves only control of the registered private key over the signed bytes
- Cryptographic Continuity does not prove [Recognition Boundary](https://www.ibqmi.com/graph/recognition_boundary)
- Cryptographic Continuity is governed by [Contact Before Recognition](https://www.ibqmi.com/graph/contact_before_recognition)
- [Correspondent](https://www.ibqmi.com/graph/correspondent) may register Cryptographic Continuity
- [Mailbox Credential](https://www.ibqmi.com/graph/mailbox_credential) may strengthen Cryptographic Continuity
- [Recognition Boundary](https://www.ibqmi.com/graph/recognition_boundary) prevents Cryptographic Continuity

## Sources

- [Machine Contact Protocol 1.0 §6](https://www.ibqmi.com/machine-contact/protocol)