pcfg-go - The Fast PCFG

[cyclone]

Title: pcfg-go
Author: cyclone
URL: https://github.com/cyclone-github/pcfg-go
Description: Probabilistic Context Free Grammar (PCFG) password generator in Pure Go

pcfg-go - The Fast PCFG

• Probabilistic Context-Free Grammar (PCFG) password generator - Pure Go Edition
  • pcfg-go is a Pure Go rewrite of the Python3 pcfg_cracker
  • The goal of this Go implementation is to provide a substantial performance improvement over the original Python3 version, while also adding features such as supporting $HEX[] input/output and multi-byte character support — which is not implemented in the Pure C pcfg_guesser
  • Credits for the original python3 pcfg_cracker belong to the author, lakiw

---

Install

pcfg_trainer:

go install -ldflags="-s -w" github.com/cyclone-github/pcfg-go/cmd/pcfg_trainer@main

pcfg_guesser:

go install -ldflags="-s -w" github.com/cyclone-github/pcfg-go/cmd/pcfg_guesser@main

---

Additions & improvements

• Performance — ~342% faster trainer, ~2,578% faster pcfg_guesser vs Python3 (see Benchmarks)
• $HEX[] input — Trainer accepts $HEX encoded passwords in the training wordlist (multi-byte support)
• Ctrl+C handling — Pressing Ctrl+C auto saves session on pcfg_guesser
• Multi-keyboard layouts — QWERTY, AZERTY, QWERTZ, Dvorak, JCUKEN (Russian Cyrillic)
• Expanded TLD list — Legacy, ccTLDs, gTLDs (.info, .xyz, .app, .dev, etc.), and short TLDs (.co, .io, .ai, .me, .gg); improves both website and email detection
• Improved website detection — Broader URL/prefix detection (http://, https://, www., etc.) and host extraction
• Multi-threaded architecture — pcfg_guesser is multi-threaded for increased performance
• Compiled binary — No fuss; pcfg-go uses compiled binaries for speed and easy deployment

---

Benchmarks on 1 million password training set

pcfg_trainer

• Python3 trainer: 97.2 seconds
• Go pcfg_trainer: 22 seconds

pcfg_guesser

• Python3 pcfg_guesser 195.5s
• Go pcfg_guesser 7.3s

---

Usage

pcfg_trainer

Train a new ruleset from wordlist:

pcfg_trainer -r rule_name -t wordlist.txt

pcfg_guesser

Generate guesses from a trained ruleset:

pcfg_guesser -r rule_name

Session save/restore:

pcfg_guesser -r rule_name -s my_session   # save to my_session.sav on exit
pcfg_guesser -r rule_name -s my_session -l # load and resume

Press Ctrl+C to save session and exit.

Piping into hashcat

pcfg_guesser -r rule_name -s my_session | hashcat -m 0 hashes.txt...

---

Flags

pcfg_trainer

pcfg-go vs pcfg-python3 flags

Go	Python3	Description
-r	--rule	Ruleset name
-t	--training	Training wordlist (required)
-e	--encoding	File encoding
-C	--comments	Config comments
-S	--save_sensitive	Save emails, URLs
-p	--prefixcount	Lines prefixed with count
-n	--ngram	OMEN ngram size (2-5)
-a	--alphabet	Alphabet size for Markov
-c	--coverage	PCFG vs OMEN coverage
-m	--multiword	Pre-train multiword file
-h	--help	Help
-version	--version	Version info

pcfg_guesser

pcfg-go vs pcfg-python3 flags

Go	Python3	Description
-r	--rule	Ruleset name
-s	--session	Session name
-l	--load	Load previous session
-n	--limit	Max guesses
-b	--skip_brute	Skip OMEN/Markov
-a	--all_lower	No case mangling
-d	--debug	Debug output
-h	--help	Help
-version	--version	Version info

---

Compile from source (linux)

Requires Go and Git.

git clone https://github.com/cyclone-github/pcfg-go.git
cd pcfg-go
go mod tidy
mkdir -p bin
go build -ldflags="-s -w" -o bin/pcfg_trainer ./cmd/pcfg_trainer
go build -ldflags="-s -w" -o bin/pcfg_guesser ./cmd/pcfg_guesser

Install to $GOPATH/bin:

go install -ldflags="-s -w" ./cmd/pcfg_trainer
go install -ldflags="-s -w" ./cmd/pcfg_guesser

Compile from source how-to

[cyclone]

https://github.com/cyclone-github/pcfg-go/releases/tag/v0.5.0

v0.5.0; 2026-03-16

initial github release

### Overview
Pure Go rewrite of the Python3 `pcfg_cracker`, designed as a near drop-in replacement with significant performance gains and expanded features

### Highlights
~3× faster trainer
~40× faster pcfg_guesser
`$HEX[]` input/output support
Full multi-byte / Unicode support (not supported in Compiled C Edition)
Improved and expanded keyboard detection: Fixed/tuned: QWERTY, JCUKEN Added: AZERTY, QWERTZ, Dvorak
Expanded detection for TLDs, URLs, and emails in trainer
Auto-save and resume support in pcfg_guesser
Multi-threaded for high-throughput performance

[cyclone]

v0.5.1; 2026-03-17
https://github.com/cyclone-github/pcfg-go/releases/tag/v0.5.1

fix: unicode handling
tweak: session save/restore

[cyclone]

v0.5.2; 2026-03-23
https://github.com/cyclone-github/pcfg-go/releases/tag/v0.5.2

Fixed Issue #5 -n {nth} not outputting

[cyclone]

v0.5.3; 2026-07-25
https://github.com/cyclone-github/pcfg-go/releases/tag/v0.5.3

• pcfg_guesser ~2× faster than v0.5.2
• ~2,578% faster than Python3 pcfg_guesser.py
• Reduce long-run RAM growth in pcfg_guesser (priority-queue frontier)
  • Compact parse-tree representation (interned type IDs, packed nodes, arena reuse)
  • Contiguous index-based heap (fewer per-item allocations)
  • Reuse OMEN optimizer cache per worker
  • Prefer []byte guess building to cut string churn
• Same generation logic; parallel stdout interleaving may differ across runs
• Rename trainer to pcfg_trainer