Dev trades CTF fun for quantum dread: builds python beast SecureVault to foil 'harvest now, decrypt later' hackers—in 20 years

A developer, inspired by cryptography challenges on platforms like pwn.college, CryptoHack, and picoCTF, created SecureVault, a cross-platform file encryption tool. The tool addresses the "harvest now, decrypt later" threat model, where encrypted files can be stored and potentially decrypted in the future using advanced quantum computers. SecureVault combines classical elliptic-curve Diffie-Hellman and post-quantum key encapsulation mechanisms to protect against long-term quantum risk. The tool uses a hybrid design, encrypting files with symmetric encryption and protecting the key exchange layer with both classical and post-quantum cryptography. SecureVault signs the entire encrypted package, including metadata, and verifies signatures during decryption to prevent silent corruption. The project, available on PyPI and as a GUI download, demonstrates a defense-in-depth approach to cryptography, acknowledging that no system is future-proof. The developer learned that cryptography is about assumptions and that hybrid designs can reduce risk, and plans to continue improving SecureVault based on community feedback.