CS-MAST-S Signature Format

CS-MAST-S is a PHC-style string (inspired by the PHC String Format) that encodes both the configuration parameters and the cryptographic hash of the node.

---

Structure

$v=<version>$<params>$<hashHex>

Section	Example	Description
$v=<version>	$v=1	Spec version — always 1 for this implementation
$<params>	$hash=sha256,lang=js,...	Comma-separated key=value pairs
$<hashHex>	$a3f2b1...	64-character lowercase SHA-256 hex digest

Full example

$v=1$hash=sha256,lang=js,lver=es6,prsr=-babel/parser,scat=lit_val_decl,sinc=IfStatement$a3f2b1c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2

---

Parameters

Parameters appear in the second $-delimited section, comma-separated in this order:

Key	Required	Value	Example
hash	yes	Hash algorithm	hash=sha256
lang	yes	Language extension	lang=js
lver	no	Language version	lver=es6
prsr	yes	Sanitized parser name	prsr=-babel/parser
scat	*	_-joined category codes	scat=lit_val_decl
sinc	*	_-joined node type names	sinc=IfStatement_ForStatement

*At least one of scat or sinc must be present.

prsr Sanitization

Characters outside [a-zA-Z0-9/+.-] are replaced with -:

Input	Stored as
@babel/parser	-babel/parser
tree-sitter/python	tree-sitter/python
my parser v2	my-parser-v2

Multi-value separator

Both scat and sinc use underscore (_) to join multiple values:

scat=lit_val_id_name_decl
sinc=IfStatement_ForStatement_WhileStatement

---

No Salt

The PHC string format specifies a salt field; CS-MAST intentionally omits it. CS-MAST is designed for deterministic subtree matching — a salt would break the property that the same source code always produces the same signature. Password security is not a goal here.

---

Hashmap Key

The full PHC string (all three sections) is the hashmap key used by cs_mast_s_exists. This means signatures from different configurations (different scat, lang, lver, etc.) never collide in the lookup table.

---

Codebase-Level Signature

When using cs_mast_init_codebase, a codebase-level signature is produced. It uses the same config params but a different hashHex:

codebaseHash = sha256(sorted([h1, h2, ...]).join(''))

File order is irrelevant — the sort ensures a deterministic result regardless of the order files are passed to cs_mast_init_codebase.

---

Codec

import { parseSignature, buildSignature } from '@shriyanss/cs-mast';

// Parse
const sig = '$v=1$hash=sha256,lang=js,prsr=-babel/parser,scat=lit$' + 'a'.repeat(64);
const parsed = parseSignature(sig);
// → { version: 1, hash: 'sha256', lang: 'js', prsr: '-babel/parser',
//     scat: ['lit'], sinc: [], hashHex: 'aaa...' }

// Build
const rebuilt = buildSignature({
  version: 1, hash: 'sha256', lang: 'js', prsr: '-babel/parser',
  scat: ['lit'], sinc: [], hashHex: 'a'.repeat(64),
});
// → '$v=1$hash=sha256,lang=js,prsr=-babel/parser,scat=lit$aaa...'

parseSignature returns null for any of these invalid inputs:

• Missing required fields (hash, lang, prsr)
• Both scat and sinc absent
• hashHex not exactly 64 lowercase hex characters
• Wrong version (not v=1)
• Malformed PHC structure (wrong number of $ sections)