Cryptography and Data Verification

Importance in Cryptography

• Ensures data authenticity when sent to a third party.
• Similar to signing a contract with a signature for verification.

Key Concepts

Non-repudiation

• Ensures data can be verified as coming from the sender.

Proof of Integrity

• Verify data consistency and accuracy.
• Uses hashing (message digest or fingerprint).
• Modifying data results in a different hash.

Hashing Example

• Project Gutenberg Encyclopedia Volume 1 (8.1 MB) example.
• Changing one character alters the hash.
• Allows detection of data modifications.

Proof of Origin

• Verifies the sender of the data.
• Often used in digital signatures.

Digital Signatures

Non-repudiation and Authentication

• Ensures message origin.
• Uses private and public key cryptography.
• Similar to signing with pen and paper.

Process

1. Alice and Bob Example:
   • Alice sends a message "You're hired, Bob."
   • Alice adds a digital signature.
2. Hashing:
   • A hash of the text is created.
3. Encryption with Private Key:
   • Alice encrypts the hash with her private key.
4. Message Transmission:
   • Bob receives the message with the digital signature.
5. Verification by Bob:
   • Bob uses Alice’s public key to decrypt the signature.
   • Compares decrypted hash with generated hash from received data.
   • If hashes match, verifies authenticity and origin.

Conclusion

• Digital signatures provide proof of integrity and origin.
• Understanding this process aids in comprehending cryptographic integrity and transaction authenticity.