Mathematics I / Number Theory in Action
Practice question · Fill in the blanks

Complete the source of RSA's security.

RSA is secure because ______.

Word bank: its algorithm is kept secret · factoring a large product of two primes is computationally hard · modular exponentiation is impossible to compute · the primes it uses are small

Hints
  1. One option would break the system entirely if it were true, since encryption itself needs that operation.
  2. The secret is a pair of numbers, not a procedure.
Show the answer

RSA is secure because factoring a large product of two primes is computationally hard.

Why

Security comes from a hard mathematical problem, not concealment. Modular exponentiation must be EASY, it is how encryption works, while its inverse, factoring, must be hard. Small primes would be factored instantly, which is why real keys use enormous ones.

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