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ZWMath›Elementary number theory›Primes and cryptography›RSA cryptosystem›ZW-RSA-CRYPTOSYSTEM-002
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AreaNumber theoryCourseElementary number theoryTopicPrimes and cryptography
Divisibility and factorization10
  • Bézout's identity
  • Extended Euclidean algorithm
  • Euclid's lemma
  • Fundamental theorem of arithmetic
  • Least common multiple
  • Infinitude of primes
  • Linear Diophantine equation
  • Greatest common divisor Discrete mathematics
  • Euclidean algorithm Discrete mathematics
  • Prime number Discrete mathematics
Congruences9
  • Complete residue system
  • Modular inverse
  • Linear congruence
  • Chinese remainder theorem
  • Fermat's little theorem
  • Euler's totient function
  • Euler's theorem
  • Wilson's theorem
  • Modular congruence Discrete mathematics
Orders and quadratic residues6
  • Multiplicative order
  • Primitive root
  • Quadratic residue
  • Legendre symbol
  • Euler's criterion
  • Law of quadratic reciprocity
Arithmetic functions5
  • Multiplicative arithmetic function
  • Divisor functions
  • Perfect number
  • Möbius function
  • Möbius inversion formula
Continued fractions and Diophantine equations4
  • Continued fraction
  • Convergent of a continued fraction
  • Pell's equation
  • Sum of two squares
Primes and cryptography3
  • RSA cryptosystem
  • Fermat primality test
  • Prime number theorem

Exercise · ZW-RSA-CRYPTOSYSTEM-002 · ★☆☆ Basic

If p = 5 and q = 7, what is the value of n?

Choose one option.

Show answer
  • A. 35

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Explanation

The modulus is n = pq = 5·7 = 35. The option equal to the product of p and q is correct.

Study Elementary number theory in ZWMath →

Review the concept: RSA cryptosystem

The RSA cryptosystem is a public-key encryption method based on the difficulty of factoring the product of two large primes. It uses Euler's theorem and modular inverses to encrypt and decrypt messages.

\[c \equiv m^{e} \pmod{n}, \quad m \equiv c^{d} \pmod{n}\]

More practice problems: rsa cryptosystem

  • ZW-RSA-CRYPTOSYSTEM-001 Which modulus is used to compute the exponent d in RSA?
  • ZW-RSA-CRYPTOSYSTEM-003 For p = 5 and q = 7, what is the value of φ(n)?
  • ZW-RSA-CRYPTOSYSTEM-004 What condition must the public exponent e satisfy in RSA?
  • ZW-RSA-CRYPTOSYSTEM-005 Which theorem guarantees that m^ed ≡ m pmodn in RSA?
  • ZW-RSA-CRYPTOSYSTEM-006 With p = 3, q = 11 and e = 3, find d such that 3d ≡ 1 (mod 20).
  • ZW-RSA-CRYPTOSYSTEM-007 With n = 33 and d = 7, what is the decryption of c = 31?
  • ZW-RSA-CRYPTOSYSTEM-008 If e = 5 and φ(n) = 24, what is the modular inverse d of e?
  • ZW-RSA-CRYPTOSYSTEM-009 With p = 5 and q = 11, compute φ(n) and the smallest valid exponent e = 3.

← ZW-RSA-CRYPTOSYSTEM-001 ZW-RSA-CRYPTOSYSTEM-003 →

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