Cryptography & Security
Intermediate
Euler's Totient
Counts integers below n coprime to it, for n = pq — used to make RSA keys.
Formula
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φ(n)Totient
pPrime factor
qPrime factor
Example
p=3, q=11: φ = 2×10 = 20
Did You Know?
Choosing e coprime to φ(n) and finding its inverse d is exactly how an RSA key pair is generated.
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