Which cryptographic algorithm uses the product of two large prime numbers?

Which cryptographic algorithm uses the product of two large prime numbers?

• A. Elliptic Curve Cryptography
• B. Digital Signature Algorithm
• C. RSA Cryptosystem
• D. Advanced Encryption Standard

Answer: (C)

The key idea here is that RSA builds its public-key system from the product of two large primes. In RSA, you pick two big primes and multiply them to form the modulus n. This semiprime n is used in both the public and private keys, and the security rests on the difficulty of factoring n back into p and q. Elliptic Curve Cryptography relies on the difficulty of the elliptic curve discrete logarithm problem, not on factoring a product of primes. The Digital Signature Algorithm uses primes and modular arithmetic, but the security basis isn’t the product of two primes forming a modulus in the same way. Advanced Encryption Standard is a symmetric algorithm with no prime-product modulus involved. So the algorithm that explicitly uses the product of two large primes is RSA.

The key idea here is that RSA builds its public-key system from the product of two large primes. In RSA, you pick two big primes and multiply them to form the modulus n. This semiprime n is used in both the public and private keys, and the security rests on the difficulty of factoring n back into p and q. Elliptic Curve Cryptography relies on the difficulty of the elliptic curve discrete logarithm problem, not on factoring a product of primes. The Digital Signature Algorithm uses primes and modular arithmetic, but the security basis isn’t the product of two primes forming a modulus in the same way. Advanced Encryption Standard is a symmetric algorithm with no prime-product modulus involved. So the algorithm that explicitly uses the product of two large primes is RSA.