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Brand-New Hash Function BeeM A. Satoh SCIS2006 SHA-1 Broken! Prof. Xiaoyun Wang.
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Transcript of Brand-New Hash Function BeeM A. Satoh SCIS2006 SHA-1 Broken! Prof. Xiaoyun Wang.
Brand-New Hash FunctionBrand-New Hash FunctionBrand-New Hash FunctionBrand-New Hash Function
BeeMA. Satoh
SCIS2006
SHA-1 Broken!
Prof. Xiaoyun WangProf. Xiaoyun Wang
SCIS2006
Essential Characteristics of Hash Function
Hash Function– Algorithm that compresses an arbitrarily size of message into a fixed size
hash value. It is also called a message digest function.
– Used for authentication, error detection, and pseudo-random number generators
One-Wayness– It is easy to generate the hash value from a given message,
but it is computationally infeasible to generate a message producing a given hash value.
Collision Resistance– It is computationally infeasible to generate a message pair that
has the same hash value.
SCIS2006
Birthday Attack
In a group of 40 people, a pair who have the same birthday can be found with 89% probability
When a hash value size is n bits, a collision can be found in 2n/2 messages with 50% probability
Birthday Paradox
SCIS2006
ExampleOne-wayness is also satisfied
Collision Resistance againstBirthdayAttack
Birthday
Brand-New Hash FunctionBrand-New Hash Function
SCIS2006
Bye-Bye My LoveBye-Bye My Love