暗号学的ハッシュ関数
データを固定長のユニークな文字列（デジタル指紋）に変換するアルゴリズム。
In blockchain, hash functions link blocks together (the hash of the previous block is included in the current block), creating an immutable chain. They also protect passwords, verify file integrity, and enable digital signatures.
graph LR
Center["暗号学的ハッシュ関数"]:::main
Pre_cryptography["cryptography"]:::pre --> Center
click Pre_cryptography "/terms/cryptography"
Pre_computer_science["computer-science"]:::pre --> Center
click Pre_computer_science "/terms/computer-science"
Pre_algorithm["algorithm"]:::pre --> Center
click Pre_algorithm "/terms/algorithm"
Rel_bitcoin["bitcoin"]:::related -.-> Center
click Rel_bitcoin "/terms/bitcoin"
Rel_blockchain["blockchain"]:::related -.-> Center
click Rel_blockchain "/terms/blockchain"
Rel_proof_of_work["proof-of-work"]:::related -.-> Center
click Rel_proof_of_work "/terms/proof-of-work"
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🧒 5歳でもわかるように説明
どんなに大きな本やビデオでも、それをギュッと一つの短いコードにする「魔法の機械」です。中身が1文字でも変わると、コードも全然違うものになります。
🤓 Expert Deep Dive
Cryptographic hash functions like SHA-256 and Keccak-256 are the workhorses of blockchain. They underpin Proof of Work (finding a hash below a target), Merkle Trees (efficient data verification), and Address Generation (deriving public keys). Security depends on Pre-image Resistance (difficult to find input from output) and Collision Resistance (difficult to find two inputs with same output). As quantum computing advances, older standards like MD5 and SHA-1 have been deprecated due to collision vulnerabilities, driving the move towards SHA-3 and quantum-safe algorithms.