CipherMail

About

Features

    Encrypt Emails: Secure your emails with OpenPGP encryption
    Decrypt Emails: Read encrypted emails directly in Gmail
    Sign Messages: Digitally sign your emails for authenticity
    Verify Signatures: Automatically verify signatures on received messages
    Key Server Lookup: Search for recipient public keys on HKP servers
    Key Management: Generate, export, import, and rotate your PGP keys
    Secure Storage: Your private keys are encrypted with AES-256-GCM

Security

    RSA-4096 bit key generation
    AES-256-GCM encryption for local key storage
    PBKDF2 with 310,000 iterations for key derivation
    Brute-force protection (5 attempts = 30 min lockout)
    Passphrase strength validation
    Automatic clipboard clearing
    Session timeout

The extension is open sourced.