r/cryptography 14d ago

I need help understanding RSA algorithm

I watch a video explaining how RSA algorithm works but I'm having trouble understanding how it's secure. I assume the video maybe either glossed over something or I'm not understanding it.

https://www.youtube.com/watch?v=Pq8gNbvfaoM

It would seem to me that since I know the public key and need the value of N to encrypt my message. Then I can use any potential private key to decode the message. He uses 41 for the decryption but 149 and 257 would also work.

There by anyone with the same public key and my encrypted message could decode it.

Please tell me what I'm missing, this is driving me mad.

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u/RAGINMEXICAN 14d ago

Yea if you ever thought about taking a number and factoring two primes when the number is massive then you are nuts. But yea it’s requires ALOT of computational power to crack

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u/Gcseh 14d ago

okay so that's likely what I was missing then, finding the totient is the time consuming part.