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Daily Challenges

Test your cryptography knowledge and earn XP

Daily Challenge Resets in 23:59:59

Today's Challenge

In modular arithmetic, what is the smallest positive integer x that satisfies the equation below?

7x ≡ 1 (mod 13)

Hint: You're looking for the modular multiplicative inverse of 7 modulo 13.

Practice Challenges

Modular Arithmetic +50 XP

Basic Modulo

Calculate the remainder when 247 is divided by 17.

247 mod 17 = ?
Prime Numbers +75 XP

Prime Check

Is 91 a prime number? Enter 1 for Yes, 0 for No.

Is 91 prime?
Modular Arithmetic +100 XP

Power Mod

Calculate 3 raised to the power of 4, modulo 11.

3^4 mod 11 = ?
Prime Numbers +75 XP

Prime Factorization

What is the smallest prime factor of 143?

143 = ? × ...
Discrete Logs +150 XP

Find the Exponent

Find x where 2^x mod 13 = 8

2^x ≡ 8 (mod 13)
Elliptic Curves +200 XP

Curve Point

For y² = x³ + 7 (mod 11), is (2, 7) on the curve? Enter 1 for Yes, 0 for No.

Check: 7² ≡ 2³ + 7 (mod 11)?