Posts tagged #Signature
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The rule, the watermark and the pen
From August 2026, text generated by Anthropic's models will carry a statistical watermark, in compliance with Article 50 of the EU AI Act. How you watermark a sequence of words (logits, softmax, entropy: the signal lives where the model is undecided), what that signal actually says and how well it holds up: a paraphrase dissolves it, a positive can be forged, open models run locally never apply it; with a test replicated locally, a watermark inserted, measured and removed on a half-billion-parameter model. And the question the watermark does not answer: a text is always someone's work of synthesis, and what makes it reliable is the process, the sources, the responsibility of whoever signs it, not the pen it was written with. Do the watermark, and the rule that requires it, add anything to the reliability of content, or do they risk creating misunderstandings? Where it speaks of editorial responsibility, the rule itself suggests the answer.
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The number used only once
Every digital signature consumes, besides the key, a second secret number generated for the occasion and good only once: the nonce. If it repeats, two signatures give back the private key with a subtraction: it happened to the PlayStation 3 and to Bitcoin wallets on Android in 2013. How the recovery works in ECDSA and in Schnorr, shown on the bytes of real signatures; why a nonce that is merely predictable betrays as well; and the point that concerns Bitcoin: a node validates a signature born from a disastrous nonce like any other, consensus cannot notice.
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Bitcoin and quantum computing
A quantum computer will not be able to rewrite Bitcoin's ledger: it will probably be able, one day, to open some of its locks. What Shor's and Grover's algorithms actually do, why elliptic curve signatures are the target and hashes are not, which coins already have their public key in view (about 35% of the circulating supply, recounted on our own node) and which do not, where the machines stand with dates attached, where the post-quantum migrations under discussion stand (BIP-360, BIP-361), and why the hard part is not technical but a matter of governance: what to do with the coins of those who can no longer move them. A snapshot declared as of July 2026.
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A fingerprint and a clock no one controls
A fingerprint says whether a text has changed, a clock no one can move lets one establish when this text existed, a stable signature says who it comes from: three already-known tools, put together, that do not abolish trust but shift it from whoever publishes to what anyone can check. A concrete use case, not a showcase of buzzwords.