PyLCG

Ultra-fast Linear Congruential Generator for IP Sharding

PyLCG is a high-performance Python implementation of a memory-efficient IP address sharding system using Linear Congruential Generators (LCG) for deterministic random number generation. This tool enables distributed scanning & network reconnaissance by efficiently dividing IP ranges across multiple machines while maintaining pseudo-random ordering.

Features

• Memory-efficient IP range processing
• Deterministic pseudo-random IP generation
• High-performance LCG implementation
• Support for sharding across multiple machines
• Zero dependencies beyond Python standard library
• Simple command-line interface

Installation

pip install pylcg

Usage

Command Line

pylcg 192.168.0.0/16 --shard-num 1 --total-shards 4 --seed 12345

As a Library

from pylcg import ip_stream

# Generate IPs for the first shard of 4 total shards
for ip in ip_stream('192.168.0.0/16', shard_num=1, total_shards=4, seed=12345):
    print(ip)

How It Works

Linear Congruential Generator

PyLCG uses an optimized LCG implementation with carefully chosen parameters:

Name	Variable	Value
Multiplier	a	1664525
Increment	c	1013904223
Modulus	m	2^32

This generates a deterministic sequence of pseudo-random numbers using the formula:

next = (a * current + c) mod m

Memory-Efficient IP Processing

Instead of loading entire IP ranges into memory, PyLCG:

1. Converts CIDR ranges to start/end integers
2. Uses generator functions for lazy evaluation
3. Calculates IPs on-demand using index mapping
4. Maintains constant memory usage regardless of range size

Sharding Algorithm

The sharding system uses an interleaved approach:

1. Each shard is assigned a subset of indices based on modulo arithmetic
2. The LCG randomizes the order within each shard
3. Work is distributed evenly across shards
4. No sequential scanning patterns

Performance

PyLCG is designed for maximum performance:

• Generates millions of IPs per second
• Constant memory usage (~100KB)
• Minimal CPU overhead
• No disk I/O required

Benchmark results on a typical system:

• IP Generation: ~5-10 million IPs/second
• Memory Usage: < 1MB for any range size
• LCG Operations: < 1 microsecond per number

Contributing

Performance Optimization

We welcome contributions that improve PyLCG's performance. When submitting optimizations:

1. Run the included benchmark suite:

python3 unit_test.py

2. Include before/after benchmark results for:

• IP generation speed
• Memory usage
• LCG sequence generation
• Shard distribution metrics

3. Consider optimizing:

• Number generation algorithms
• Memory access patterns
• CPU cache utilization
• Python-specific optimizations

4. Document any tradeoffs between:

• Speed vs memory usage
• Randomness vs performance
• Complexity vs maintainability

Benchmark Guidelines

When running benchmarks:

1. Use consistent hardware/environment
2. Run multiple iterations
3. Test with various CIDR ranges
4. Measure both average and worst-case performance
5. Profile memory usage patterns
6. Test shard distribution uniformity

Roadmap

• IPv6 support
• Custom LCG parameters
• Configurable chunk sizes
• State persistence
• Resume capability
• S3/URL input support
• Extended benchmark suite

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