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Why does SHA-256d (double SHA-256) in Bitcoin have a constrained message schedule in the second hash?

Bitcoin mining uses SHA-256d: SHA-256(SHA-256(data)) . I recently discovered experimentally (IACR ePrint 2026/109079) that the second SHA-256 application has a structurally constrained message schedule: The second hash always receives exactly 32 bytes (the first hash output) + fixed Merkle-Damgård padding This makes W[8-15] in the second hash always constant (0x80000000... + length encoding) Only 30 unique carry patterns exist in the second hash vs theoretical 2^64 Measurable cross-hash anti-correlation: 9.56σ (confirmed real, scales as √N) My questions: Was this structural property of SHA-256d considered when Bitcoin adopted double-SHA-256? Or was it chosen purely for length-extension attack resistance? Is there any documentation of this constrained W-schedule effect in Bitcoin's design rationale? Does this property have any known implications for Bitcoin's security model beyond length-extension resistance? The correlation is not exploitable (r=0.03, ...
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where is bitcoind and bitcoin-cli

i recently downloaded bitcoin core via https://bitcoincore.org/bin/bitcoin-core-31.0/ i downloaded: bitcoin-31.0-arm64-apple-darwin.zip when i unzipped it, it created the bitcoinqt app. i was expecting it to create a folder directory like below: bitcoin-31.0/ ├── bin/ │ ├── bitcoind │ ├── bitcoin-cli │ └── ... because i want to use bitcoind, not bitcoinqt. before it always created a bitcoind and the other stuff. now i just see the bitcoinqt app. from Recent Questions - Bitcoin Stack Exchange https://ift.tt/ov1KH7E via IFTTT
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Ledgersys — Tomorrow's Finance, Today

Why does every Bitcoin tax tool accept credit cards but not Bitcoin? I built one that fixes this. from Recent Questions - Bitcoin Stack Exchange https://ift.tt/6pYBzOU via IFTTT
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What factors make a location suitable for Bitcoin mining beyond low electricity cost?

Electricity price is often cited as the primary factor in choosing a mining location. However, I’m curious what other technical or operational factors should be considered, such as grid stability, cooling efficiency, or infrastructure reliability. How do these variables impact long-term mining performance and profitability? from Recent Questions - Bitcoin Stack Exchange https://ift.tt/tS1wEYV via IFTTT
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Why Bitcoin is not starting to act on quantum threat?

How come Bitcoin community is not acting on this huge threat? They keep saying it is a FUD instead of getting together and coming up with ideas. Without proper roadmap Bitcoin will be eliminated within next 4 years! https://www.coindesk.com/tech/2026/03/28/watch-out-bitcoin-devs-google-says-post-quantum-migration-needs-to-happen-by-2029 from Recent Questions - Bitcoin Stack Exchange https://ift.tt/x2DUzWP via IFTTT
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What are the options for issuing tokens natively on Bitcoin without a sidechain?

I'm familiar with Liquid and Rootstock to issue tokens on Bitcoin, but they require trusting a separate system like a federation or a separate chain. Is there a way to issue fungible tokens directly on Bitcoin and Lightning, without relying on a sidechain or a trusted federation? from Recent Questions - Bitcoin Stack Exchange https://ift.tt/h8uCYSn via IFTTT
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Does inserting a Tapret commitment leaf invalidate the existing control block for other script paths in RGB?

I'm researching how RGB uses Taproot commitments (Tapret, LNPBP-12) and ran a transfer experiment on testnet: 64a14551...c20b6b . The RGB client output shows the state anchored at tapret1st:64a14551...c20b6b:1 — a standard P2TR output on-chain. My understanding is that Tapret inserts an unspendable 64-byte OP_RETURN leaf into the script tree at depth 1, shifting existing scripts one level deeper. This changes the Merkle root, which changes the output key (P2TR address) via the BIP-341 tweak formula. Two questions: If Script_A was originally at depth 1 (single-leaf, empty Merkle path in the control block), after Tapret insertion it moves to depth 2. Does the original control block become invalid? Does the spender need to reconstruct it with the Tapret leaf hash included in the Merkle path? Since the Merkle root changes with every new Tapret commitment, does RGB always derive a fresh P2TR address for each state transition — even if the internal key P remains the same? ...
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