← Back to the reading view
Slides · 12 slides
Hash functions & digital signatures
The same module told visually, ready to present. Speaker notes carry the full explanation.
Foundations
Hash functions & digital signatures
One-way fingerprints for data, and how they prove a message is authentic and untampered
Hash functions & digital signatures · Classical Crypto Today1 / 12
Any size in, fixed size out
What a hash function does
Hash functions & digital signatures · Classical Crypto Today2 / 12
Avalanche effect
One letter in, a completely different digest out
Hash functions & digital signatures · Classical Crypto Today3 / 12
Retire, don't reuse
Broken versus current
Hash functions & digital signatures · Classical Crypto Today4 / 12
Inside SHA-2
Merkle–Damgård: a chain of compression steps
Hash functions & digital signatures · Classical Crypto Today5 / 12
The side effect
Length extension: pick up where the chain stopped
Hash functions & digital signatures · Classical Crypto Today6 / 12
Go deeper · padding
SHA-256 padding for a 13-byte message
Hash functions & digital signatures · Classical Crypto Today7 / 12
In practice
How to avoid length extension
Hash functions & digital signatures · Classical Crypto Today8 / 12
2015 · SHA-3
A structurally different design
Hash functions & digital signatures · Classical Crypto Today9 / 12
The birthday bound
Why 256 bits gives 128-bit collision resistance
Hash functions & digital signatures · Classical Crypto Today10 / 12
Signatures
Hash, then sign
Hash functions & digital signatures · Classical Crypto Today11 / 12
Keyed hashing
HMAC: two nested hashes
Hash functions & digital signatures · Classical Crypto Today12 / 12
1 / 12
Keys: ← → move, F full screen, G all slides, N notes