How does AES GCM encryption work • Previously utilized AES…

How does AES GCM encryption work

• Previously utilized AES CBC 256 encryption with a 256-bit key and 128-bit IV, but experienced performance issues.
• Transitioned to AES GCM encryption using a 256-bit key and 96-bit IV to enhance performance.
• The authentication tag is crucial for both AES GCM encryption and decryption; it can be prepended to the ciphertext for convenient access during decryption.
• There are concerns regarding the necessity of hiding the auth tag from attackers; it is generally not considered sensitive like the ciphertext.
• Reusing an IV can result in repeated patterns in encrypted ciphertexts, even with different messages, due to identical letters.
• Reusing an IV in CBC mode poses risks, but in GCM mode, it can be catastrophic, particularly if the same IV is used for multiple messages from a single sender.
• "AuthenticatedData" in AES GCM refers to additional data that is authenticated but not encrypted, ensuring the integrity and authenticity of the data.
• For further details on AuthenticatedData in AES GCM, consult the Apple Developer documentation.