Do C2PA Content Credentials do the same job as a dated record?
No. They overlap a little, but they answer different questions. C2PA Content Credentials are a provenance label attached to a file: which tool made it, what edits were done, whether generative AI was involved, signed so that tampering shows. A dated record, like the one OpenStela keeps, sits outside the file: it fixes that these exact bytes existed by a certain date, under a name you chose, with your own description of what you did, and it can be looked up by anyone who has the file.
So the short version is: Content Credentials tell a viewer how a file came to be. A dated record tells a viewer when it existed and who claimed it. Neither one decides who owns the work. If you make images, video or audio with AI tools, it's worth understanding both, because your tools may already be adding the first one, and the second one can break if you're not careful about which copy you register.
What C2PA and Content Credentials are
The Coalition for Content Provenance and Authenticity (C2PA) describes itself, on c2pa.org, as providing "an open technical standard for publishers, creators and consumers to establish the origin and edits of digital content." Its steering committee lists Adobe, Amazon, BBC, Google, Meta, Microsoft, OpenAI, Publicis Groupe, Sony, TikTok and Truepic (checked 2026-11-12).
"Content Credentials" is the friendly name for a C2PA manifest. From the C2PA 2.2 explainer (part of the C2PA Specifications 2.2 release, May 2025; newer versions up to 2.5 are listed on the spec site):
- A manifest contains "one or more assertions, which are statements about the asset, such as its origin." Those can record the tool that created the file, edits made, and whether AI was involved.
- The manifest is bound to the file with standard cryptographic hashes such as SHA2-256, chained together and "finally digitally signed." Change the pixels and the binding no longer matches.
- "The C2PA Manifest is commonly embedded directly within the asset," though it can also be found externally through watermarks or fingerprint lookup.
The technical specification adds that a manifest can carry a time-stamp from a Time Stamp Authority, which shows "that the signature itself actually existed at a certain date and time." So a C2PA file can carry a date too. That matters for the comparison below.
What Content Credentials don't do
The C2PA documents are refreshingly direct about their limits. Three are worth knowing before you rely on them.
They don't judge whether the story is true. The explainer says Content Credentials "do not provide value judgments about whether a given set of provenance data is 'true', but instead merely whether the provenance information is well-formed and free from tampering." A valid manifest means nobody altered the label after signing. It doesn't mean the label is correct.
They don't identify you by default. Per the explainer, the specification "does not directly address the topic of human or organizational identity," which it frames as respecting privacy. Extensions exist for adding identity. The signer is whoever holds the certificate used to sign, which is often the software that produced the file rather than you.
They can be removed. Asked whether provenance metadata can be removed, the explainer answers: "Yes it can." That's why the standard also defines "durable" credentials, which pair the hash with a watermark or fingerprint so a stripped file can be matched back to a manifest stored elsewhere. Whether a given file has that depends on the tool that made it.
None of this is a flaw. C2PA was built to help viewers understand media they encounter, especially as AI makes fakes cheap. It wasn't built to be a registry of who made what, or to hold your statement of what you contributed.
What a dated record does
A dated record works from the outside. Here is what happens when you register a work on OpenStela, checked against our own code on 2026-11-12:
- You upload the file (mp3, m4a, wav, jpg, png, webp, mp4 or webm) or register a link to a published page.
- We compute the SHA-256 fingerprint of the exact bytes you uploaded. The file is stored as-is; we don't re-encode works you register.
- You fill in an authorship record: the name you publish under, the date you say you made it, the tools you used, a rights declaration, and, if AI was involved, a description of your own contribution. That last field is required for AI works.
- The record, with the fingerprint inside it, is hashed and frozen. Afterward you can change only the title, a note and whether it's public.
- That night the record's hash goes into a Merkle tree whose root is written to Arbitrum One.
- Anyone can paste the file's fingerprint into the verify page, and you can download a Proof Pack with the record, its Merkle proof and the chain transaction, enough to recompute everything without us.
What it doesn't do matches the C2PA list in spirit. We don't read or check Content Credentials. We don't judge the content of the work or whether your contribution text is accurate. It's your statement, dated. And the record shows that a file existed by a date, not that you hold the rights to it. What a character ID proves, and what it doesn't goes through that line in detail.
Side by side
| C2PA Content Credentials | A dated record (OpenStela) | |
|---|---|---|
| Where it lives | Usually inside the file | Outside the file, keyed on its fingerprint |
| Who writes it | The tool or app that signs the manifest | You, through your account |
| What it describes | Origin, edits, AI involvement | The file's fingerprint, your name, stated date, tools, your contribution, rights |
| Date | Optional time-stamp from a time-stamp authority | Registration time, anchored in that night's batch |
| Your identity | Not part of the core spec; extensions exist | The name you publish under and an account number |
| If the file is re-saved | Manifest may be lost or stop matching | The record stays; the new file has a new fingerprint |
| Who checks it | Anyone with the file and a C2PA viewer | Anyone with the file or fingerprint; offline from the Proof Pack |
| Does it decide ownership or truth? | No | No |
Checked 2026-11-12 against the C2PA 2.2 explainer and specification and OpenStela's code.
Where they collide: the bytes
There's one practical trap. An embedded manifest is part of the file's bytes. A fingerprint covers all the bytes. So the same picture with and without its Content Credentials is, as far as SHA-256 is concerned, two different files.
That shows up in ordinary ways:
- You export a PNG from a tool that adds Content Credentials, then open it in an editor that doesn't keep them and save again. The new copy has no manifest and a new fingerprint.
- A social platform re-encodes your image on upload. Many do. The copy people download from there won't match the file you registered. (OpenStela does this too, for images attached to posts: they're re-encoded to strip EXIF. Registered works are not.)
- You register the raw export first, then run it through a tool that adds Content Credentials before publishing. Now the published copy and the registered copy differ.
None of these breaks anything, as long as you know which copy is which. The record still proves the registered bytes existed on its date. You just need to be able to hand over that copy.
Using both, in order
A sensible routine for an AI image or video you're about to release:
- Keep the original export untouched. If your tool attached Content Credentials, leave them in. Don't re-save through software that drops them. Check what's there with a C2PA viewer such as verify.contentauthenticity.org.
- Register that exact file. The fingerprint now covers the image and its manifest together, and your authorship record sits next to it with your stated contribution, which a manifest has no field for.
- If you edit it into a final version, register that too, and mark it as a later version of the first. OpenStela records that link as its own dated entry, so the sequence (raw output on one date, finished piece on a later one) is visible.
- Publish wherever you like. If the platform strips the credentials, that's fine. Your registered originals still carry them, and the records are unaffected.
- Keep the files and the Proof Pack together. The record can only be matched against the bytes it was made from.
If the work belongs to a character, bind it after registering. The background on why a date matters at all is in Five ways to prove a file existed on a date, and the free, account-free alternative for the dating part is covered in Is OpenTimestamps enough, or do I need a registry?.
On cost: registering works is free within 300 MB of storage per account and a daily limit. The only fee is on sales: 5% (minimum $15) to the seller when a deal reaches the transfer step. See pricing.
This is general information, not legal advice.
C2PA 內容憑證跟日期紀錄是同一件事嗎？
不是。兩者有一點重疊，但回答的是不同的問題。C2PA 內容憑證（Content Credentials）是貼在檔案上的「來源標籤」：哪個工具做的、做過哪些編輯、有沒有用到生成式 AI，再加上數位簽章，事後被竄改就看得出來。日期紀錄（例如 OpenStela 做的這種）則放在檔案外面：它固定「這份一模一樣的檔案，在某一天之前就已經存在」，附上你選的署名、你自己寫的貢獻說明，而且手上有檔案的人都能查。
一句話：內容憑證告訴看的人這個檔案「怎麼來的」；日期紀錄告訴看的人它「哪天就有了、誰出面登記」。兩者都不決定作品歸誰。如果你用 AI 工具做圖、做影片、做音樂，兩個都值得搞懂——你的工具可能早就在幫你加前者，而後者如果登記錯了版本，之後會對不起來。
C2PA 跟內容憑證是什麼
C2PA 的全名是 Coalition for Content Provenance and Authenticity（內容來源與真實性聯盟）。它在官網 c2pa.org 上的自我介紹是：提供「一套開放的技術標準，讓發布者、創作者與一般使用者可以確認數位內容的來源與編輯紀錄」。指導委員會名單列有 Adobe、Amazon、BBC、Google、Meta、Microsoft、OpenAI、Publicis Groupe、Sony、TikTok 與 Truepic（2026-11-12 查證）。
「內容憑證」就是 C2PA manifest（清單）比較好懂的叫法。以下整理自 C2PA 2.2 版說明文件（屬 C2PA Specifications 2.2，2025 年 5 月；規格網站上目前已列到 2.5 版）：
- 一份 manifest 包含「一或多個 assertion（聲明），也就是關於這個檔案的陳述，例如它的來源」。可以記錄產生檔案的工具、做過的編輯、有沒有 AI 參與。
- manifest 用 SHA2-256 這類標準雜湊跟檔案綁在一起，一層包一層，「最後再加上數位簽章」。像素一改，綁定就對不上。
- 「C2PA manifest 通常直接嵌在檔案裡」，也可以透過浮水印或指紋比對，從外部找回來。
技術規格本文另外提到，manifest 可以帶一個由時戳機構（Time Stamp Authority）發的時間戳，用來證明「簽章本身在某個日期時間確實已經存在」。也就是說，C2PA 檔案本身也可以帶日期——這點在後面的比較很重要。
內容憑證做不到的事
C2PA 自己的文件把限制寫得很坦白。依賴它之前，有三點要先知道。
它不判斷內容是不是真的。 說明文件寫得很清楚：內容憑證「不對來源資料是否『真實』做價值判斷，只判斷這些來源資訊格式是否正確、有沒有被竄改」。manifest 驗證通過，代表標籤簽完之後沒人動過，不代表標籤寫的是對的。
它預設不標示你是誰。 依說明文件，規格「沒有直接處理個人或組織身分的問題」，理由是尊重隱私；要加上身分，得靠延伸規格。簽章的人是持有簽章憑證的一方，很多時候是產生檔案的那套軟體，而不是你本人。
它可以被拿掉。 對於「來源資訊能不能被移除？」，說明文件的回答是：「可以。」所以標準另外定義了「耐久型」（durable）內容憑證：把雜湊跟浮水印或指紋配在一起，檔案裡的 manifest 被剝掉之後，還能從別處存放的 manifest 比對回來。你的檔案有沒有這一層，要看產生它的工具。
這些都不是缺點。C2PA 的目的，是在 AI 讓造假變便宜的年代，幫看的人理解眼前這張圖、這支影片是怎麼來的。它本來就不是「誰做了什麼」的登錄簿，也沒有欄位讓你寫下自己貢獻了什麼。
日期紀錄做的事
日期紀錄是從檔案外面處理。以下是在 OpenStela 登記一件作品時實際發生的事（2026-11-12 對照我們自己的程式確認）：
- 上傳檔案（mp3、m4a、wav、jpg、png、webp、mp4、webm），或登記一個已公開頁面的連結。
- 我們對你上傳的原始位元組算 SHA-256 指紋。檔案原樣存放，登記的作品不會被重新編碼。
- 你填一張著作紀錄：公開發表用的署名（可用筆名）、你主張的創作日期、用了哪些工具、權利聲明；如果有 AI 參與，還要寫下你自己做了什麼——AI 作品這一欄是必填。
- 紀錄（指紋就在裡面）算出雜湊後凍結。之後能改的只剩標題、備註和公開與否。
- 當晚，紀錄的雜湊進入 Merkle 樹，樹根寫上 Arbitrum One。
- 任何人都能把檔案指紋貼到查驗頁查；你也能下載 Proof Pack，裡面有紀錄本體、Merkle 證明路徑和鏈上交易，不靠我們也能自己重算。
它做不到的事，精神上跟 C2PA 那份清單很像：我們不讀、也不驗證內容憑證；不判斷作品內容，也不查你寫的貢獻說明是否屬實——那是你自己的陳述，只是被加上了日期。紀錄證明的是「某個檔案在某天之前已經存在」，不證明你有權利。這條界線在編號證明什麼、不證明什麼有完整說明。
並排比較
| C2PA 內容憑證 | 日期紀錄（OpenStela） | |
|---|---|---|
| 放在哪裡 | 通常嵌在檔案裡 | 檔案外，以檔案指紋為索引 |
| 誰寫的 | 簽署 manifest 的工具或 App | 你，透過自己的帳號 |
| 記錄什麼 | 來源、編輯、AI 參與 | 檔案指紋、署名、主張的日期、工具、你的貢獻、權利聲明 |
| 日期 | 選配：時戳機構的時間戳 | 登記時間，當晚批次上鏈 |
| 你的身分 | 核心規格不處理，有延伸規格 | 你發表用的署名＋帳號編號 |
| 檔案被另存之後 | manifest 可能消失或對不上 | 紀錄還在；新檔案是新指紋 |
| 誰能查 | 有檔案＋C2PA 檢視工具的人 | 有檔案或指紋的人；Proof Pack 可離線重算 |
| 會決定歸屬或真假嗎 | 不會 | 不會 |
2026-11-12 對照 C2PA 2.2 說明文件、技術規格與 OpenStela 程式查證。
兩者會打架的地方：位元組
實務上有一個陷阱。嵌在檔案裡的 manifest，本身就是檔案位元組的一部分；而指紋涵蓋所有位元組。所以同一張圖「有內容憑證」和「沒有內容憑證」，對 SHA-256 來說就是兩個不同的檔案。
日常會遇到的情況：
- 你從會加內容憑證的工具匯出一張 PNG，再丟進不保留憑證的修圖軟體另存。新檔案沒有 manifest，指紋也變了。
- 社群平台上傳時重新壓縮你的圖——很多平台都會。別人從那裡下載的版本，跟你登記的檔案對不上。（OpenStela 的貼文附圖也會這樣：為了去掉 EXIF 一律重新編碼。登記的作品則不會。）
- 你先登記原始輸出，發表前才用工具加上內容憑證。這時公開的版本和登記的版本就不一樣了。
這些都不會壞事，前提是你清楚哪一份是哪一份。紀錄依然證明「登記的那份位元組」在那天就存在，你只要拿得出那一份就好。
怎麼一起用：照這個順序
一張準備發表的 AI 圖或一支 AI 影片，建議這樣做：
- 原始匯出檔不要動。 工具有附內容憑證就留著，不要用會丟掉憑證的軟體另存。可以用 verify.contentauthenticity.org 這類 C2PA 檢視工具看看裡面有什麼。
- 登記那一份檔案。 指紋會連同圖片和 manifest 一起涵蓋，旁邊再加上你的著作紀錄與貢獻說明——這是 manifest 沒有欄位可放的東西。
- 後製出完成版，也登記， 並標註它是前一件的後續版本。OpenStela 會把這個關聯記成一筆獨立、有日期的紀錄，「哪天有原始輸出、哪天完成」的時序就看得到。
- 想發哪裡就發哪裡。 平台剝掉憑證也沒關係：你登記的原檔還帶著，紀錄也不受影響。
- 檔案和 Proof Pack 放在一起保存。 紀錄只能拿當初那份位元組來比對。
如果作品屬於某隻角色，登記之後再綁上去就好。為什麼「日期」這件事重要，背景請看證明檔案在某天存在的五種方法；只想處理日期、又不想開帳號的免費做法，請看OpenTimestamps 就夠了，還是需要登錄簿？。
費用：作品登記免費，但有額度——每個帳號 300 MB 作品空間，另有每日登記上限。唯一的收費在成交時：交易走到移轉那一步，向賣方收 5%（最低 US$15）。詳見價格。
本文為一般資訊，不是個案法律意見。
Questions常見問題
My AI tool already adds Content Credentials. Is that enough?我的 AI 工具已經會加內容憑證，這樣就夠了嗎？
It depends on what you need. Credentials tell a viewer the file came from that tool and whether it was edited. They don't hold your account of what you contributed, they're often signed by the tool rather than you, and they can be stripped. If you want a dated, outside record with your name and your contribution in it, register the file as well.
看你要什麼。憑證告訴看的人：這個檔案出自那個工具、有沒有被編輯過。它不記錄你自己貢獻了什麼，簽章的常常是工具而不是你，而且可以被拿掉。如果你要的是一份在檔案外、有日期、寫著你的署名與貢獻的紀錄，就另外登記。
Does registering on OpenStela remove the Content Credentials?在 OpenStela 登記，會把內容憑證弄掉嗎？
No. Uploaded works are stored byte for byte, so an embedded manifest stays in our copy. We don't read or verify it, though. Images attached to social posts are a different path: those are re-encoded to strip EXIF, so don't rely on a post to keep credentials.
不會。上傳的作品逐位元組原樣存放，嵌在裡面的 manifest 會留在我們的副本裡——不過我們不讀、也不驗證它。社群貼文的附圖是另一條路：為了去除 EXIF 會重新編碼，所以別指望貼文保留憑證。
Does a C2PA time-stamp do the same thing as anchoring?C2PA 的時間戳跟上鏈是同一件事嗎？
Both put a date on a signature or a hash. A C2PA time-stamp comes from a time-stamp authority and travels inside the file's manifest, so it's lost if the manifest is. An anchored record keeps its date outside the file, and its Merkle root is on a public chain that anyone can check.
兩者都是替簽章或雜湊加上日期。C2PA 時間戳由時戳機構發出，跟著 manifest 存在檔案裡；manifest 不見，它就跟著不見。上鏈的紀錄把日期放在檔案外，Merkle 樹根寫在公開的鏈上，任何人都能查。
Which copy should I register if the platform strips credentials on upload?平台上傳會剝掉憑證，那我該登記哪一份？
Register the original you exported, with its credentials. That's the copy you control and can hand over later. If you also need the published copy on record, register it separately and mark it as a later version of the original.
登記你自己匯出、帶著憑證的原檔。那是你能掌握、之後拿得出來的版本。如果公開版也需要留紀錄，就另外登記一次，並標註它是原檔的後續版本。