AES-GCM is a method combining both encryption of data and authentication of that data using a [[MAC]]. It takes in: 1. An IV (12 bytes) 2. A symmetric key (32 bytes) 3. Data to encrypt 4. An optional unencrypted data "tag" that helps provide a variant of the encrypted data (using a stable identifier both sides can agree on). For [[ECIES Hybrid Encryption]], AES-GCM can take on both the encryption and the [[MAC]] side of things. # Weaknesses Though generally considered very strong, researchers have found a problem with [[Fast Mesage Franking]], which is used in end-to-end encrypted systems as part of abuse reporting processes. A paper suggests a concept called [[Encryptment]] to address this.