anti
66c73ce59d
Per-session 64-bit SimHash of inter-keystroke digraph flight times: walk single-char input events, accumulate flight time per (c1,c2), bucket the median, Charikar-SimHash the bucketed pairs. Locality- sensitive so the same typist is Hamming-close across sessions; pastes and think-pauses break the chain; silent below the sample-size floor. New shared decnet/util/simhash.py (simhash64/hamming64/bytes helpers). Registered as a conditional Tier-A primitive (count 37->38); requires behave-shell>=0.1.2.
67 lines
2.1 KiB
Python
67 lines
2.1 KiB
Python
# SPDX-License-Identifier: AGPL-3.0-or-later
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"""Charikar 64-bit SimHash + Hamming helpers.
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Locality-sensitive fingerprint: inputs that share most weighted tokens
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produce hashes a few bits apart (small Hamming distance), so near-
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duplicates cluster without storing the raw feature vector. Used by the
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keystroke-digraph biometric (``decnet/profiler/.../motor.py``) and the
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campaign clusterer's typing-similarity edge.
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ponytail: ``templates/smtp/server.py:_body_simhash`` is the same
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algorithm, inlined to keep slim decky containers from importing decnet.
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Left as-is to avoid pulling decnet into decky images; dedup here only if
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a third caller appears.
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"""
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from __future__ import annotations
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import hashlib
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from collections.abc import Mapping
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_BITS = 64
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_MASK = (1 << _BITS) - 1
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def simhash64(weighted_tokens: Mapping[str, int]) -> int:
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"""Charikar 64-bit SimHash over frequency-weighted tokens.
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Returns 0 on empty/all-zero-weight input — callers treat 0 as "no
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signal". Per-token hash is md5[:8]: a content fingerprint, not a
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security primitive.
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"""
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if not weighted_tokens:
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return 0
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bits = [0] * _BITS
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for tok, weight in weighted_tokens.items():
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if weight <= 0:
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continue
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h = int.from_bytes(
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# Content fingerprint, not a security primitive — md5[:8] is fast
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# and 64 bits is all we need; usedforsecurity=False clears B324.
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hashlib.md5(
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tok.encode("utf-8", errors="replace"), usedforsecurity=False,
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).digest()[:8],
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"big",
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)
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for i in range(_BITS):
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bits[i] += weight if (h >> i) & 1 else -weight
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out = 0
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for i in range(_BITS):
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if bits[i] > 0:
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out |= (1 << i)
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return out
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def hamming64(a: int, b: int) -> int:
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"""Number of differing bits between two 64-bit ints."""
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return ((a ^ b) & _MASK).bit_count()
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def to_bytes8(value: int) -> bytes:
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"""64-bit int → 8 big-endian bytes (for ``BINARY(8)`` storage)."""
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return (value & _MASK).to_bytes(8, "big")
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def from_bytes8(raw: bytes) -> int:
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"""8 big-endian bytes → 64-bit int."""
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return int.from_bytes(raw, "big")
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