Posts tagged #Nonce
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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.