The Bitcointalk exchange
Forum user 'bdonlan' had asked whether running SHA-256 twice in a row — the double hash that secures every Bitcoin transaction — could introduce a weakness. It was a fair question. In cryptography, layering algorithms can sometimes create unexpected vulnerabilities. But Satoshi's answer was clear: the double hash is a feature, not a bug.
" Danish: "Udvekslingen på Bitcointalk
Forumbrugeren 'bdonlan' havde spurgt, om det at køre SHA-256 to gange i træk – det dobbelte hash, der sikrer hver Bitcoin-transaktion – kunne introducere en svaghed. Det var et rimeligt spørgsmål. Inden for kryptografi kan lagdeling af algoritmer nogle gange skabe uventede sårbarheder. Men Satoshis svar var klart: det dobbelte hash er en funktion, ikke en fejl.
" Note: "the double hash" -> "det dobbelte hash" (hash is neuter? In Danish, "hash" is often neuter: "et hash", so "det dobbelte hash". "feature, not a bug" -> "en funktion, ikke en fejl" (common translation in tech). Third paragraph: "Satoshi's reasoning
Satoshi explained that double SHA-256 actually increases the security margin. Even if one of the hash functions were to be broken in the future, the second layer would still protect the network. The design was intentional, a hedge against advances in cryptanalysis. At the time, the idea of quantum computers breaking SHA-256 seemed distant. Today, it's a live research topic.
" Danish: "Satoshis begrundelse
Satoshi forklarede, at dobbelt SHA-256 faktisk øger sikkerhedsmarginen. Selv hvis en af hashfunktionerne skulle blive brudt i fremtiden, ville det andet lag stadig beskytte netværket. Designet var bevidst, en sikring mod fremskridt inden for kryptoanalyse. På det tidspunkt virkede ideen om kvantecomputere, der bryder SHA-256, fjern. I dag er det et aktivt forskningsemne.
" Note: "a hedge against" -> "en sikring mod" (hedge = afdækning, but here it's a safeguard). "advances in cryptanalysis" -> "fremskridt inden for kryptoanalyse". "live research topic" -> "aktivt forskningsemne". Fourth paragraph: "Quantum computing and double hashing
Bitcoin's reliance on double SHA-256 is often cited as a reason the network might survive a quantum attack longer than single-hash systems. Satoshi's 2010 post laid out the logic before most people had even heard of quantum computing. The post didn't mention quantum specifically, but the principle — defense in depth — applies directly. Researchers now study how double hashing could delay a quantum adversary, buying time for a network upgrade.
" Danish: "Kvantecomputere og dobbelt hashing
Bitcoins afhængighed af dobbelt SHA-256 nævnes ofte som en grund til, at netværket kan overleve et kvanteangreb længere end systemer med enkelt hash. Satoshis indlæg fra 2010 lagde logikken frem, før de fleste overhovedet havde hørt om kvantecomputere. Indlæget nævnte ikke kvante specifikt, men princippet – forsvar i dybden – gælder direkte. Forskere studerer
