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Cryptographic watermarking A signed mark inside the content.

A cryptographic watermarkCryptographic watermarking: A hidden mark that carries or points to a signed record, so a check gives a yes or no rather than a likelihood. is a signed code hidden in the content itself. A checker reads it and answers yes or no: who signed it, and whether it changed since. It is a record you can check, not a guess.

Start freeCheck a file
A signed text mark gives a yes or no anyone can check, valid or changed; a statistical pattern runs through a model and gives a probability, such as 72 percent likely AI.
A cryptographic mark gives a checkable answer. A statistical pattern gives a probability.
Signed
It carries a digital signatureDigital signature: Math that shows which key signed something and that it has not changed since. Any edit to the signed bytes breaks it.. Change one word and the check fails.
Hidden
Readers see the same words. In text, the mark is a run of characters that draw nothing.
Free to check
Anyone can check it at no cost, with no account.
Yes or no
A check says valid, changed, or no mark found. There is no percent score.
Not forever
Retyping, rewriting, or a tool that strips hidden characters removes it.

Metadata, cryptographic watermark, statistical watermark

All three get called labels or marks. They answer different questions. A statistical watermarkStatistical watermarking: A hidden pattern a model adds while generating content, found later by a detector that returns a likelihood. such as SynthIDSynthID: Google DeepMind's statistical watermark, added while a model generates content and read by Google's detector. is a pattern, not a record.

Three ways to mark content
C2PA metadataCryptographic watermarkStatistical watermark
Where it livesBeside the content, as metadataMetadata: Data stored beside the content in a file, such as author, camera or date. Many tools strip it when they copy or upload a file. in the fileInside the content, as hidden charactersSpread through the words or pixels as a pattern
What a check saysValid, changed, or missingValid, changed, or missingA likelihood that the pattern is there
Names who signedYesYesNo. It points to a model's pattern
A tool strips metadataLostKept, unless hidden characters are stripped tooKept
Words are rewrittenCheck failsLost for the rewritten wordsWeakens. Heavy rewrites can remove it
Who can checkAnyone, with open toolsAnyone, free, in a public checkerThe provider, with its own detector

Encypher uses the first two together. The EU Code of PracticeCode of Practice on AI-generated content: The EU's voluntary rulebook on marking and labeling AI content, published in final form on June 10, 2026. on AI labels asks for layers like these.

Hard binding and soft binding

C2PAC2PA: The Coalition for Content Provenance and Authenticity: the group that publishes the open standard for content labels., the open standard for content labels, ties a label to content in two ways: a hard bindingHard binding: A hash of the content's signed bytes stored in the label, so a change to those bytes makes the check fail. and a soft bindingSoft binding: A watermark or fingerprint that can find a content label again after the file was copied or its metadata stripped..

Hard binding is a fingerprint of the exact file, so a re-encode breaks it. Soft binding is a watermark in the picture that still leads back to the label after a re-encode.
The fingerprint proves the file is unchanged. The watermark finds the label again when the file has changed or lost it.
Hard binding
A hashHash: A short fingerprint of exact bytes. Any change, even one character, gives a completely different hash. of the exact bytes, sealed in the signed label. A change to the hashed content fails the check. Excluded metadata and supported label updates may not.
Soft binding
A watermarkWatermark: A mark placed in the content itself, visible or hidden, so it can be found again after the file is copied. or fingerprintFingerprinting: Computing a compact summary of content and matching it against a database to find copies. in the content itself. It lasts through some edits and leads back to the label when the metadata is gone.

Labels in plain text

Readers see only the words of a paragraph: The town pool opens Monday at noon. Lifeguards are on duty until 6 p.m. A faint gold stitch under the lines stands for the signed label carried unseen inside the words. A checker reads it back: signed by Town Daily, made with AI: no, unchanged since signing.
The signed label travels inside the words without changing how they look. Anyone can check who signed, what they declared about AI, and whether the text changed.

Plain text has no file wrapper to hold a label. So the signed record travels inside the text itself, in characters readers do not see. Copy the words and the label goes with them.

A quoted sentence can also be checked on its own against the signed article.

Text watermarking in detail

Images, audio, video and documents

A file signed with a label and a watermark loses its label when a site strips metadata; a checker finds the watermark, which points back to the signed record, shown as recovered.
If a site strips the label, a supported watermark can lead back to the signed record. The result says it was recovered.

For files, including PDF and Word documents, the label is a C2PA manifestC2PA manifest: The signed label itself: a small package inside a file that records who signed it, what they declared and how to check it. stored inside the file. A hard binding ties it to the exact bytes. Some platforms strip it when they resize or re-encode. A supported watermark can then lead a checker back to the record.

How a stripped label is found again

Where the mark stays, and where it is lost

A text mark is kept through copy and paste, wire feeds and scrapers; sometimes lost in social posts and text cleanup; and lost when the text is rewritten or printed.
The mark rides the exact characters. Tools that copy text as-is keep it; retyping or stripping invisible characters loses it.
Kept
Copy and paste in browsers and editors, publishing in a CMS, wire feeds and web scrapers. They copy characters as they are.
Sometimes lost
Some email, chat and social tools strip hidden characters.
Lost
Retyping, paraphrasing, translating or a screenshot makes new text with no mark.

The full list, tool by tool

Why a signed mark matters

AI labels
Article 50Article 50: The EU AI Act rule that AI-made content be marked in a form software can read, and deepfakes disclosed. of the EU AI ActEU AI Act: The European Union's law on artificial intelligence, which includes rules for marking AI-made content. asks AI makers to mark output in a form machines can read. It applies from August 2, 2026, and from December 2, 2026 for systems already on sale.

Questions

What is cryptographic watermarking?
A cryptographic watermark is a signed code hidden inside the content. A checker reads it and says who signed the content and whether it changed. The answer is valid, changed or no mark found, never a percent score.
How is it different from a statistical watermark like SynthID?
A statistical watermark is a pattern a model leaves while it writes. A detector estimates whether the pattern is there. A cryptographic watermark is a signed record that either checks out or does not. The two can be used together.
Does it survive copy and paste?
Yes, in tools that copy text as it is, such as web browsers and most editors. Some email and social tools strip invisible characters, and a retyped or rewritten copy carries no mark.

For engineers

Show the technical detail

For text, the C2PA standard for unstructured textC2PA text-provenance standard: The part of the C2PA standard that puts a signed label inside plain text, using invisible Unicode characters. defines how a signed manifest is carried inside the text as invisible UnicodeUnicode: The standard that gives every character in every writing system a number, so text looks the same on every device. characters. The signature covers a hash of the visible words, so a changed word fails the check.

Encypher can also sign each sentence, so a quoted sentence can be checked against the signed article on its own. This sentence-levelSentence-level attribution: Checking that one sentence came from a specific signed source unchanged, even when it is quoted on its own. layer is patent-pending.

For files, manifests sit in JUMBFJUMBF: JPEG Universal Metadata Box Format: the container that holds a C2PA label inside a media file. boxes at the format's standard location and are signed with COSE and an X.509 certificateX.509 certificate: A digital ID card for a signing key: it names the holder and is itself signed by a certificate authority. chain. Encypher authored C2PA's standard for unstructured text, published as Section A.7 in C2PA 2.3 and carried forward as Section A.8 in C2PA 2.4.

Full technical walkthrough

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