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How is RSA encryption calculated in practice?

I understand the number theory behind RSA primes, totient function, modular inverse. But when I look at real code or standards like PKCS#1, there are many more steps. I'm asking about the bridge from the elegant mathematical concept to the actual, secure software that gets deployed and used every day.

 

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By Kriya Answered 2 years ago

In practice, implementing RSA involves careful steps beyond the basic math. First, key generation uses a strong random number generator for large primes p and q. We then compute n and φ(n). Choosing e is often simplified to 65537 for efficiency and security. The modular inverse for d is computed via the Extended Euclidean Algorithm. Crucially, raw textbook RSA is insecure; I always recommend using a standard padding scheme like OAEP before the modular exponentiation (m^e mod n). In real systems, libraries handle these steps using optimizations like the Chinese Remainder Theorem for fast decryption.

 

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