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AskDeveloper Podcast - 49 - Cryptography - Part 3 - Digital Signaures and Protocols

AskDeveloper Podcast - 49 - Cryptography - Part 3 - Digital Signaures and Protocols

○ Digital Signatures
§ Goal: verify Authenticity of a message.
§ Based on Asymmetric Cryptography.
§ Basic operations
1. Public / Private keys generation (using some algorithm like RSA)
2. Signing algorithm using the private key
3. Signature verification algorithm using the corresponding public key
i. Extending previous Example
• Steps (Order is very important, bold stuff is the difference added to authenticate sender)
® Party 1 (Alice)
1. Generates a random AES Session Key (32 bytes / 256 bits)
2. Generates a random Initialization Vector (IV) (16 bytes / 128 bits)
3. Encrypt the message to be sent using the AES Session Key & IV
4. Calculate an HMAC of the encrypted message using the AES Session key
5. Encrypt the AES Session Key using the Public Key of Party 2 (Bob) The recipient.
6. Calculate Signature using the private signing key on the HMAC
7. Sends a packet of (Encrypted Message, Encrypted Session Key, Ini

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