One thing cryptography articles never seem to explain is how the message actuall
ID: 648469 • Letter: O
Question
One thing cryptography articles never seem to explain is how the message actually gets encrypted. You get this long-winded lecture on number theory which ends with, Ta Da! and we have a public and private key. Then, they never explain the process of exactly how some 100,000 byte word document gets encrypted using the public key.
Other times the explanations seem downright misleading. For example, in my book Cryptography (by Meyer and Matyas) it says for RSA the ciphertext is the plain text to the power of key. How do you exponentiate a word document? I don't get it.
Explanation / Answer
Well, exponentiating a word document is rather easy. As you've said, it's 100,000 bytes, or 800,000 bits. This word document can thus be interpreted as a number between 0 and 2800000. Sure this number may be large, but it can be exponentiated.
However, more commonly symmetric encryption is used with a 128 or 256 bit key to encrypt the word document, and then public-key encryption is used on that key, as number between 0 and 2256. This approach is much faster.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.