Discuss the role of digital signatures in modern communication

Digital signatures are central to securing modern communication. They provide cryptographic assurance for the origin, integrity, and authenticity of digital information.

• Authenticity and Origin Authentication: A digital signature confirms the sender's identity and the document's origin. This prevents impersonation. For example, if Alice digitally signs an email, Bob can verify that Alice, not an imposter, sent it.
• Integrity: Digital signatures ensure data has not been altered since it was signed. Any change to the message, even a single bit, causes signature verification to fail. This protects against accidental corruption or malicious modification during transmission.
• Non-repudiation: Once a message is digitally signed, the sender cannot credibly deny sending it. This offers irrefutable proof of origin, which is important for legal and commercial transactions.

Digital signatures use a hash function to create a unique message digest. The sender then encrypts this digest with their private key, forming the digital signature. The recipient uses the sender's public key to decrypt the signature. They then compute their own hash of the received message. If the decrypted hash matches the computed hash, the signature is valid, confirming authenticity and integrity.