Pith Number

pith:MQB2XUF2

pith:2026:MQB2XUF2N7GH5GOMCZBVGVGCPA

not attested not anchored not stored refs pending

PACZero: PAC-Private Fine-Tuning of Language Models via Sign Quantization

Marten van Dijk, Murat Bilgehan Ertan, Phuong Ha Nguyen, Srinivas Devadas, Xiaochen Zhu

PACZero achieves usable fine-tuning performance for large language models at zero mutual information privacy by using sign quantization to create unanimous gradient updates.

arxiv:2605.06505 v2 · 2026-05-07 · cs.LG · cs.AI · cs.CR

Open paper page JSON Open Graph Bundle Merged state Verified badge What is a Pith Number?

Add to your LaTeX paper

\usepackage{pith}
\pithnumber{MQB2XUF2N7GH5GOMCZBVGVGCPA}

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Record completeness

1 Bitcoin timestamp

2 Internet Archive

3 Author claim open · sign in to claim

4 Citations open

5 Replications open

✓ Portable graph bundle live · download bundle · merged state

The bundle contains the canonical record plus signed events. A mirror can host it anywhere and recompute the same current state with the deterministic merge algorithm.

Claims

C1strongest claim

On SST-2 OPT-1.3B full fine-tuning at I=0, PACZero-ZPL reaches 88.99±0.91, within 2.1pp of the non-private MeZO baseline (91.1 FT). No prior method produces usable utility in the high-privacy regime ε<1.

C2weakest assumption

That sign-quantizing subset-aggregated zeroth-order gradients creates frequent unanimity steps at which every candidate subset agrees on the update direction, making the released sign cost zero conditional mutual information.

C3one line summary

PACZero achieves zero mutual information privacy for LLM fine-tuning via sign-quantized zeroth-order gradients, delivering near-non-private accuracy on SST-2 and SQuAD at I=0.

Receipt and verification

First computed	2026-05-26T02:04:12.314302Z
Builder	pith-number-builder-2026-05-17-v1
Signature	Pith Ed25519 (`pith-v1-2026-05`) · public key
Schema	pith-number/v1.0

Canonical hash

6403abd0ba6fcc7e99cc16435354c2783006a832cb9f145f687c8e63a84fefa9

Aliases

arxiv: 2605.06505 · arxiv_version: 2605.06505v2 · doi: 10.48550/arxiv.2605.06505 · pith_short_12: MQB2XUF2N7GH · pith_short_16: MQB2XUF2N7GH5GOM · pith_short_8: MQB2XUF2

Agent API

Resolver JSON Graph JSON Events JSON Schema Signing key

Verify this Pith Number yourself

curl -sH 'Accept: application/ld+json' https://pith.science/pith/MQB2XUF2N7GH5GOMCZBVGVGCPA \
  | jq -c '.canonical_record' \
  | python3 -c "import sys,json,hashlib; b=json.dumps(json.loads(sys.stdin.read()), sort_keys=True, separators=(',',':'), ensure_ascii=False).encode(); print(hashlib.sha256(b).hexdigest())"
# expect: 6403abd0ba6fcc7e99cc16435354c2783006a832cb9f145f687c8e63a84fefa9

Canonical record JSON

{
  "metadata": {
    "abstract_canon_sha256": "10ea4d6835e476e66b872d0bd2e2c77dc0b4de83eeb0609c1f40fcf168c2e341",
    "cross_cats_sorted": [
      "cs.AI",
      "cs.CR"
    ],
    "license": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
    "primary_cat": "cs.LG",
    "submitted_at": "2026-05-07T16:20:20Z",
    "title_canon_sha256": "4afda9e9e538af6078b31b61b06534fd7fd1fe29c57341832d6b815c2db4a9aa"
  },
  "schema_version": "1.0",
  "source": {
    "id": "2605.06505",
    "kind": "arxiv",
    "version": 2
  }
}