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Cryptography inside blockchains: hashing, Merkle trees, and signatures
The same module told visually, ready to present. Speaker notes carry the full explanation.
In practice
Cryptography inside blockchains
No new cryptography: the same hashes and signatures, composed into a tamper-evident structure
Cryptography inside blockchains: hashing, Merkle trees, and signatures · Classical Crypto Today1 / 6
Tamper evidence
Edit one block, break every later link
Cryptography inside blockchains: hashing, Merkle trees, and signatures · Classical Crypto Today2 / 6
Inclusion proofs
Merkle trees
Merkle tree of four transactions
Root = Hash(H12 + H34)
H12 = Hash(H1 + H2)
H1 = Hash(Tx1)
H2 = Hash(Tx2)
H34 = Hash(H3 + H4)
H3 = Hash(Tx3)
H4 = Hash(Tx4)
Proving Tx2 is included needs only H1, H34, and the root — not the other transactions.
Cryptography inside blockchains: hashing, Merkle trees, and signatures · Classical Crypto Today3 / 6
Proof size
Proofs grow with log₂ of the block
Cryptography inside blockchains: hashing, Merkle trees, and signatures · Classical Crypto Today4 / 6
Self-custody
Your key is your money
Cryptography inside blockchains: hashing, Merkle trees, and signatures · Classical Crypto Today5 / 6
Post-quantum
Spent addresses reveal their public keys
Cryptography inside blockchains: hashing, Merkle trees, and signatures · Classical Crypto Today6 / 6
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