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Cryptography

Cryptography is the system of encrypting information.

Why do we need cryptography?
We need cryptography to:

  • Ensure secure communication between two parties
  • Ensure that the message is sent by the same person
  • And to prevent unauthorized access to information

Some of the methods for cryptography are:

FAQs

Why can't we trust self-signed Certificates?
We cannot trust certificates that are self-signed, because X.509 certificates are trusted based on the authenticity of the Certificate Authority (CA) issuing the certificate.

Normal communication:

  • The user verifies the certificate issued by a CA and uses it to encrypt their message
  • The server uses the private key to decrypt the message

In case of self-signed certificates, there can be a Person-in-the-middle attack:

  • The user trusts the self-signed certificate, thinking it was from the web server, and uses it to encrypt her message
  • Person-in-the-middle (Hacker) actually supplied a fake self-signed certificate to the user, who can now read her message
  • Hacker sends the message (optionally modified) by signing with the actual self-signed certificate of the website
  • Website reads the message believing the message was sent by the user

Reference: https://en.wikipedia.org/wiki/Man-in-the-middle_attack (PITM is more commonly known by the name MITM, but I prefer using the gender neutral name)

Tags:
cryptography

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