Overview

Entropy is unpredictable, public randomness that nobody can know in advance. Truestamp captures a steady stream of it from three independent public sources: the NIST Randomness Beacon, the Stellar ledger, and the Bitcoin blockchain. Each captured value becomes an entropy observation that is folded directly into the Merkle tree of an internal Truestamp block, sitting alongside the timestamped items in that same block. Because a block records values that could not have been guessed before those public events happened, the block itself becomes evidence that everything inside it was submitted after the entropy existed. This is what turns a Truestamp block into a verifiable witness of submission timing rather than a claim you simply have to trust.

Why unpredictable public entropy matters

The timing guarantee Truestamp offers is a submission window: proof that a piece of data was submitted after a known moment and before the next block. Public entropy is what makes the “after” side of that window trustworthy and hard to fake.

The key property of a good entropy source is unpredictability. You cannot know tomorrow’s Bitcoin block hash or NIST beacon value today, and once a value is published it is part of a permanent, widely replicated public record that anyone can look up. So if a Truestamp block contains a Bitcoin block hash that only came into existence at a certain time, then everything committed into that block, including your data, must have been submitted after that hash existed. It could not have been precomputed earlier, because the entropy it depends on did not yet exist.

This is deliberately a proof of submission, not of creation or authorship. Capturing a fresh entropy value alongside your data proves you submitted the data after the entropy was published. It does not prove who created the data or when it was originally written. For more on that distinction, see the submission window.

Public sources are chosen precisely because they are hard to corrupt or forge:

• No single publisher you have to trust: these beacons and blockchains are widely replicated.
• Values are cryptographically chained or signed at the source.
• Anyone in the world can independently look up the same value.
• Guessing a future value in advance is computationally infeasible.

The three sources

Truestamp captures entropy from three independent public sources. Each one has its own capture mechanism and can be turned on or off independently, so a problem at one source never blocks the others.

NIST Randomness Beacon

The NIST Randomness Beacon is a public service run by the US National Institute of Standards and Technology that publishes a fresh, cryptographically signed random value roughly once a minute, each one linked to the previous in a tamper-evident chain. Truestamp captures each new pulse by polling the beacon over HTTP and storing only the essential fields (the random output value, the chain and pulse identifiers, and the pulse timestamp), which keeps storage small while preserving enough to look the value back up in NIST’s public records.

Stellar ledger

The Stellar network closes a new ledger every few seconds, and each closed ledger carries a cryptographic hash agreed by distributed consensus. Truestamp subscribes to a live stream of these ledger events and captures the ledger sequence number, its consensus hash, and the time it closed. The ledger hash is a consensus output that no single party controls, which makes it a good unpredictable public value.

Bitcoin blockchain

Bitcoin produces a new block roughly every ten minutes, and each block hash is the output of an enormous amount of proof-of-work that cannot be predicted ahead of time. Truestamp captures new Bitcoin blocks and stores the block hash, its height, and its timestamp. Because a Bitcoin block hash is expensive to produce and impossible to know in advance, it is one of the strongest publicly verifiable “this moment has passed” signals available.

How a captured value joins a block

Every captured value becomes an entropy observation. An observation records the raw data exactly as it came from the source, together with a reproducible cryptographic fingerprint of that data. The fingerprint is computed deterministically: the raw values are canonicalized into a single, unambiguous form and then hashed, so any independent verifier who fetches the same public value can recompute the exact same fingerprint and confirm it matches.

An entropy observation is not wrapped in any intermediate record. Its composite hash becomes a leaf in the Merkle tree of a Truestamp block, directly alongside the fingerprints of the timestamped items in that same block. One combined Merkle tree covers both the items and the entropy for that block. As a result, a single block simultaneously carries your data and the public entropy that pins down when the block existed, and a proof drawn from that block can show both that your data is included and that unpredictable public entropy was captured in the same window.

Each observation moves through a simple lifecycle as it is folded in: it is first captured, then assigned to a block, and finally committed once its place in the block’s Merkle tree is fixed. Because entropy is public data, entropy observations are readable by anyone; there is no private or tenant-scoped entropy. Every observation is browsable on the public entropy pages.

Why this strengthens the guarantee

A proof cannot have been precomputed before the entropy it contains existed. That single fact is what public entropy adds to a Truestamp proof.

Without entropy, a block only establishes an internal ordering. With entropy folded in, the block is bound to concrete, externally verifiable public events. Anyone verifying a proof can independently fetch the referenced NIST pulse, Stellar ledger, or Bitcoin block from its public source, confirm the captured value is real, and conclude that the data committed in that block was submitted after those events. Capturing from three independent sources means the guarantee does not rest on any one operator or network staying honest and available.

The degree of independent confirmation available for a given observation, from recomputing its fingerprint offline to re-fetching the original value from its public source, is covered in the sibling concept on entropy verification levels.

Limitations

Public entropy proves submission timing, not creation or authorship. It shows that data was submitted after a captured value existed; it says nothing about when the data was originally created or who wrote it.

The guarantee is also only as fresh as the source. If a public source temporarily stops publishing new values, for example the NIST beacon repeating its last pulse during a US government shutdown, an independent verifier can still confirm that the captured value genuinely exists in the source’s records, but that value no longer pins the moment down as tightly. Existence remains verifiable; freshness may not, until the source resumes.