---
title: "C2SP Transparency Log Verifier"
method: POST
path: "/v1/tools/verify_c2sp_tlog_checkpoint"
tags: ["C2SP", "transparency log", "checkpoint", "signed note", "tlog-cosignature", "RFC 6962", "inclusion proof", "tlog-policy", "tlog-tiles", "Sigsum", "Rekor", "offline verifier"]
---

# C2SP Transparency Log Verifier

`POST /v1/tools/verify_c2sp_tlog_checkpoint`

## Request

- Base URL: `https://ainumbers.co`
- URL: `https://ainumbers.co/v1/tools/verify_c2sp_tlog_checkpoint`
- Auth: none declared

Verifies a C2SP checkpoint (signed note) and an RFC 6962 inclusion proof against a C2SP tlog-policy trust policy, entirely client-side. Parses the note framing, matches every signature line against the policy's log and witness keys, verifies the log signature and each tlog-cosignature, evaluates the policy quorum rule, replays the inclusion path against the root the checkpoint carries, and optionally decodes a tlog-tiles path to confirm it is the tile holding the leaf.

**Tool URL:** https://ainumbers.co/tools/625-c2sp-tlog-verifier.html

## Request body

- object
  - `checkpoint` string, required: C2SP checkpoint as signed-note text
  - `policy` string, required: C2SP tlog-policy text naming the log and witness keys and the quorum rule
  - `proof` object, required: RFC 6962 inclusion proof: leaf value, leaf index, bottom-up sibling path
  - `tile_path` string: Optional tlog-tiles path for the tile the leaf was read from

## Response `200`

Successful tool execution result

- object
  - `noteParses` boolean
  - `origin` string, nullable
  - `size` integer, nullable
  - `rootHashHex` string, nullable
  - `logKeyPinned` boolean
  - `logSignatureValid` boolean
  - `originMatchesPinnedLog` boolean, nullable
  - `witnessCosignaturesValid` integer
  - `witnessCosignatureDetail` object[]
  - `quorumRule` string, nullable
  - `witnessQuorumMet` boolean
  - `inclusionProofValid` boolean
  - `tilePathValid` boolean, nullable
  - `tileCoversLeaf` boolean, nullable
  - `ALL_PASS` boolean

---

[API](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite.md) · [All operations](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite/llms.txt) · [OpenAPI document](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite/revisions/b462e4f5bb28?raw)