Secure File Encryption Systems Using AES-256-GCM And SHA-256: A Review Of Authenticated Encryption, Key Management And Integrity Verification

Files containing academic records, financial statements, medical reports and business documents are routinely stored on laptops, removable drives and cloud folders, where they are exposed to theft, unauthorized access and silent tampering. This paper reviews the design of a secure file encryption system built on modern, standardized cryptography. The Advanced Encryption Standard with a 256-bit key in Galois/Counter Mode (AES-256-GCM) is examined as an authenticated encryption scheme that provides confidentiality and authenticity in a single operation, using a unique nonce for every encryption. The review explains why password-derived keys must be generated with a slow, salted key-derivation function such as PBKDF2 or Argon2, how the SHA-256 hash supports file integrity verification and identification, and why weaker primitives such as MD5 and SHA-1 should be avoided. A layered architecture covering the user interface, key management, cryptographic engine, integrity module and secure storage is proposed, together with an encrypted file format and a step-by-step encryption and decryption workflow. The paper also compares alternative ciphers and modes, discusses nonce misuse, key loss and post-quantum considerations, and identifies research gaps for practical tools. The review concludes that correctly combining authenticated encryption, strong key derivation and integrity checks yields a simple yet robust solution for protecting confidential files.