Plain-English definitions of the terms that come up when you need to show when a file existed: hashes, timestamps, blockchain anchoring, metadata and evidence. Each entry links to a longer guide or comparison. If you are new to the topic, start with how to prove a file existed before a date.

Terms: Anchoring · ASAP and Pooled TimeBind · Bitcoin block time · C2PA and Content Credentials · Chain of custody · Checksum · Cryptographic hash function · Digital signature · eIDAS qualified electronic time stamp · EXIF · “Existed no later than” · File integrity · File system timestamps · Hash collision · Merkle tree, Merkle root and inclusion proof · Metadata and XMP · Notarisation · OP_RETURN · OpenTimestamps · Prior art · Proof of Time Certificate · Provenance · RFC 3161 and Time Stamping Authority (TSA) · SHA-256 · Trusted timestamp

Glossary

Anchoring

Recording a hash (or a hash that summarises many hashes) in a public record that nobody can quietly rewrite, such as a block on the Bitcoin blockchain. Once anchored, the record shows that whatever produced the hash existed no later than the time of that block. See also: How verification works.

ASAP and Pooled TimeBind

The two TimeBinder priorities. An ASAP TimeBind (3 Tokens) gets its own Bitcoin transaction and can be checked directly on the blockchain without TimeBinder. A Pooled TimeBind (1 Token) is batched with other users’ hashes into one transaction; it is cheaper and slower, and checking it relies on TimeBinder’s verification service. See also: ASAP vs Pooled.

Bitcoin block time

The timestamp written into each Bitcoin block by the miner who found it. Bitcoin’s rules require it to be later than the median of the previous 11 blocks and not more than two hours ahead of the network’s time, so it is accurate to within a few hours. Because later blocks build on it, it cannot be changed afterwards without redoing the work for every later block. See also: TimeBinder vs OpenTimestamps; free blockchain timestamp options.

C2PA and Content Credentials

An open standard from the Coalition for Content Provenance and Authenticity for attaching signed provenance information (a “manifest”) to images, video, audio and documents, describing how the content was made and edited. The public label is Content Credentials. The manifest can be stripped when a file is re-saved or uploaded, and its times come from the signing tool. See also: Content Credentials vs a timestamp.

Chain of custody

The documented history of who held a piece of evidence, when, and what they did with it, from collection to presentation. For digital files, hashes taken at each hand-over show the file was not changed along the way. See also: Showing files are genuine.

Checksum

A short value calculated from data to detect accidental errors, such as CRC32 in zip files. Simple checksums catch corruption but are easy to forge on purpose, so integrity checks against deliberate change use cryptographic hashes instead. See also: Does ext4 checksum file data?.

Cryptographic hash function

A function that turns any amount of data into a fixed-length fingerprint, so that the same input always gives the same output, a tiny change gives a completely different output, and it is infeasible to find two inputs with the same output or to work back from the output to the input. SHA-256 is the most widely used. See also: Free SHA-256 file hash checker.

Digital signature

A value made with a private key that lets anyone holding the matching public key check who signed some data and that it has not changed since. A signature on its own shows who signed, not when: the signing time in most signatures comes from the signer’s own clock unless a trusted timestamp is added. See also: Signatures and dates in PDFs.

eIDAS qualified electronic time stamp

Under the EU eIDAS Regulation, a time stamp issued by a qualified trust service provider that meets set requirements. In EU member states it benefits from a legal presumption that the date and time it shows are accurate and that the data has not changed since. See also: RFC 3161 vs a blockchain timestamp.

EXIF

Metadata that cameras and phones write into photos: the date taken, camera model, lens, exposure settings and often GPS location. Its dates come from the device clock and traditionally carry no time zone, and it can be edited or stripped easily. See also: Proving a RAW photo existed; see a photo’s EXIF dates.

“Existed no later than”

The precise claim a timestamp supports. A timestamp shows that a file with a given hash existed at or before a recorded time. It cannot show when the file was first created, only that it was not created after that point. See also: How to prove a file existed before a date.

File integrity

The property that a file is exactly the same, bit for bit, as it was at an earlier point. It is checked by comparing a newly calculated cryptographic hash with one recorded earlier. See also: Check a file’s hash.

File system timestamps

The created (birth), modified, changed and accessed times that an operating system keeps for each copy of a file. They are not part of the file’s contents, change when files are copied, downloaded or unzipped, and can be edited with ordinary tools. See also: What happens to file dates when you copy a file; check a file’s dates.

Hash collision

Two different inputs that produce the same hash. For a strong function like SHA-256, no collision has ever been found, and finding one is far beyond current computing. Older functions such as MD5 and SHA-1 have practical collisions and should not be relied on for evidence. See also: SHA-256 file hash checker.

Merkle tree, Merkle root and inclusion proof

A way of combining many hashes into one. Hashes are paired and hashed together, level by level, until a single Merkle root remains. An inclusion proof is the short list of sibling hashes needed to show that one particular hash is part of a given root. TimeBinder builds a Merkle tree from a TimeBind’s file hashes and records the root on the blockchain. See also: How pooled roots work.

Metadata and XMP

Data about a file stored alongside or inside it: authors, dates, software, locations. XMP is an Adobe-created standard for embedding metadata in images, PDFs and other files. Metadata is useful context, but whoever has the file can change it. See also: Why file dates disagree; file date and metadata inspector.

Notarisation

A notary’s formal witnessing of a signature or document, usually confirming the identity of the person signing. It records a date, but notaries do not normally check the contents of digital files, and the record is held by the notary. See also: Blockchain timestamp vs a notary; Online notarization vs a timestamp.

OP_RETURN

A Bitcoin transaction output that carries a small amount of arbitrary data (typically up to 80 bytes) and cannot be spent. It is a common way to write a hash or Merkle root into the blockchain. See also: Blockchain file verification.

OpenTimestamps

An open-source protocol and set of free public servers (calendars) that batch hashes and anchor them in Bitcoin. The user keeps a small .ots proof file, which stays incomplete until the batch is confirmed and then needs upgrading. See also: TimeBinder vs OpenTimestamps.

Prior art

In patent law, evidence that an invention was already known or publicly available before a given date. Publication is what usually counts as prior art; a private dated record supports your own timeline but does not, by itself, make something public. See also: How to prove you invented something first.

Proof of Time Certificate

The PDF that TimeBinder issues for each TimeBind. It lists the TimeBind details, the Bitcoin transaction ID, the Merkle root and proof steps, and a QR code that opens the verification page. See also: Verification explained.

Provenance

The record of where something came from and what has happened to it since: who made it, who changed it, and when. For digital files it is built from metadata, version history, logs and independent records. See also: Audit trail vs provenance vs versioning.

RFC 3161 and Time Stamping Authority (TSA)

RFC 3161 is the internet standard for trusted timestamps issued by a Time Stamping Authority. You send a hash; the TSA returns a signed token stating the time it received it. Anyone can check the token, as long as they trust the TSA and its certificates remain verifiable. See also: RFC 3161 vs a blockchain timestamp.

SHA-256

A cryptographic hash function from the SHA-2 family, published by the US National Institute of Standards and Technology. It produces a 256-bit fingerprint, written as 64 hexadecimal characters. It is the hash TimeBinder calculates in your browser for each file, and the one Bitcoin itself relies on. See also: Calculate a file’s SHA-256 hash and checking a file still matches its fingerprint.

Trusted timestamp

A record, made by someone other than the file’s owner, that a particular hash existed at a particular time. It can come from a Time Stamping Authority, a public blockchain or another independent service, and turns a self-reported date into independent, verifiable evidence of when a file existed. See also: Proving a file existed before a date.

Comparisons and guides

• All comparisons: how TimeBinder compares with notaries, OpenTimestamps, RFC 3161, Content Credentials, copyright registration and more.
• How to prove a file existed before a date, with guides for specific file types.
• ASAP vs Pooled verification and pricing.

What a TimeBind shows, and what it does not. A TimeBind shows that your file existed no later than the time it was recorded on the Bitcoin blockchain, and that it still matches its fingerprint. It does not prove who created the file, that its contents are true, or how a court will treat it. It is independent evidence of timing to use alongside your other records, and it is not legal advice.

Frequently asked questions

What is the difference between a hash and a timestamp?

A hash is a fingerprint of a file’s contents and says nothing about time. A timestamp records that a hash existed at a particular time. Together they show that the exact file existed no later than that time.

Does a timestamp prove I created a file?

No. It shows that the file existed no later than the recorded time and still matches its fingerprint. Who created it has to be shown with other evidence, such as drafts, source files and communications.

Which file dates can I rely on?

File system dates and embedded metadata are useful clues but come from devices you control and change during ordinary handling. Independent records, such as a trusted timestamp or a third party’s logs, are what others can check.

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