Shouldn’t a person just RSA-encrypt the entire document?

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Tags:
Encryption
RSA
Security
After doing some research on Security, I've finally figured out how to verify if an email / document was actually sent by the "sender". Here's the process I've figured out:

  • The sender gives their public RSA key to the recipient.
  • The sender also uses SHA1 to hash the document.
  • Then he uses his private RSA key to sign the 160-bit SHA1 hash.
  • He sends the hash and document to the recipient.
  • The recipient confirms the hash with public RSA key.
  • Then he generates a SHA1 to compare the document.
  • If they hashes match, that confirms the document was from the sender.

But my question is this: Shouldn't a person just RSA-encrypt the entire document? That doesn't make sense to me.

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  • TomLiotta

    A "hash" and an "encryption" are for two different purposes.

    Shouldn't a person just RSA-encrypt the entire document?

    That depends. What do you want to accomplish? Do you want to protect the document from being read by anyone other than the recipient? Or do you want to help verify the content of the document?

    Encryption protects the document from being read by others. Hashing helps verify that the document content has not been modified.

    Tom

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