randpass

Generates passwords. One, a million, or a continuous byte stream.

Installation | Examples | Interactive Mode | Technical Details

Examples

# Basic
randpass                                 # Interactive TUI
randpass -l 20                           # 20-character password
randpass -l 16 -b                        # Copy to clipboard

# Character sets
randpass -l 32 --hex                     # Hex only (0-9, a-f)
randpass -l 20 --no-special              # Alphanumeric only
randpass -l 20 --special '_-'            # Custom special characters

# Bulk
randpass -l 32 -n 1000000 -o out.txt     # Million passwords, progress bar, interruptible
randpass -l 24 -n 1000 -o passwords.txt

# Raw bytes
randpass --bytes -n 1G -o random.bin     # 1GB to file
randpass --bytes -n 100M | xxd | head    # 100MB to stdout
randpass --bytes | dieharder -a -g 200   # Infinite stream for testing

# Command mode (save defaults)
randpass -c set -l 20 -n 5               # Save flags; future `randpass` uses them
randpass -c                              # Show saved command
randpass -c unset                        # Clear saved command

Run randpass -h for all options.

Interactive Mode

Run without arguments for the TUI.

Settings persist to ~/.config/randpass/settings.

Installation

Cargo

cargo install randpass

Pre-built Packages

Download from GitHub Releases:

# Debian/Ubuntu
sudo dpkg -i randpass_*.deb

# Fedora/RHEL
sudo rpm -i randpass-*.rpm

# Arch Linux
makepkg -si

# Generic (extract and copy)
tar xzf randpass-*.tar.gz
cp randpass-*/randpass ~/.local/bin/

Build from Source

cargo build --release
cp target/release/randpass ~/.local/bin/

Technical Details

PRNG

Uses CPU timestamp counters (rdtsc on x86_64, cntvct_el0 on ARM) mixed with a 10,000-prime table and SplitMix64 finalizer. With -u, uses a 2MB /dev/urandom pool instead. Pool read positions are scrambled per-lap using RNG state for unpredictable access patterns.

Entropy Source → rotate(17) × prime[idx] ⊕ entropy → SplitMix64 → Output

Password Generation

Character pool built from enabled classes with configurable density multipliers (e.g., lowercase_density: 2 makes lowercase 2× more likely). Pool is shuffled, then characters selected via PRNG indices.

Security

Memory protection

• Output buffers locked in RAM with mlock, preventing swap exposure
• When using /dev/urandom (-u), the 2MB pool is also mlock'd
• Core dumps disabled process-wide via PR_SET_DUMPABLE(0)
• Passwords, RNG state, and buffers zeroized with write_volatile

Urandom pool lifecycle (when -u is enabled)

• Pool allocated lazily at generation start — nothing in memory until needed
• Background refresh thread runs only during active generation
• Pool zeroized and deallocated immediately on completion
• Crash handlers (SIGSEGV/SIGABRT) emergency-zero the pool before exit

Signal handling

• SIGPIPE ignored for clean cleanup when piped (randpass --bytes | head)
• Terminal state restored on SIGINT/SIGTERM/SIGHUP
• All signal handlers use async-signal-safe operations only

I/O

• Direct write_all() avoids format string allocations in the hot path
• Escape codes suppressed when stdout is not a TTY
• Settings file stores configuration only, never passwords

Validation

Full results in rng/results/.

Platforms

License

MIT OR Apache-2.0