gbanyan
c79329457a
Splices v4 drafts into v3.20.0 master sub-files. Drops the "paper/v4/" working drafts and lands the v4.0 content in the master file structure. Internal draft notes / close-out checklists / open- questions blocks stripped at splice (per round-1 through round-6 deferral). Abstract (paper_a_abstract_v3.md): - Replaced v3.20.0 abstract (240w) with v4.0 abstract (247w). §I Introduction (paper_a_introduction_v3.md): - Replaced v3.20.0 §I with v4.0 §I (16 paragraphs + 8-item contributions list). §II Related Work (paper_a_related_work_v3.md): - Inserted v4.0 LOOO addition paragraph after the existing finite-mixture paragraph; added refs [42]-[44] to the internal reference annotation list. §III Methodology (paper_a_methodology_v3.md): - §III-A..F (Pipeline / Data / Page ID / Detection / Features / Dual Descriptors): kept v3.20.0 content unchanged. - §III-G..M: replaced v3.20.0 §III-G..K with v4.0 §III-G..M (Unit & Scope / Reference Populations / Distributional Diagnostics + composition decomposition / K=3 descriptive / Convergent internal-consistency / Anchor-based ICCR L.0-L.7 / Validation strategy + Table XXVII ten-tool collection). - §III-N Data Source & Anonymization: kept v3.20.0 §III-L content, renumbered to §III-N (after v4 §III-M). - §III-E ablation cross-reference: updated "§IV-I" -> "§IV-L" to match the renumbered §IV. - §III-F pixel-identity cross-reference: updated "§III-J" -> "§III-K". Gemini round-2 artifact paper/gemini_review_v4_round2.md also added (was uncommitted from the parallel-review batch). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Abstract
Regulations require Certified Public Accountants (CPAs) to attest each audit report with a signature, but digitization makes reusing a stored signature image across reports — through administrative stamping or firm-level electronic signing — undermining individualized attestation. We build an end-to-end pipeline detecting such non-hand-signed signatures at scale: a Vision-Language Model identifies signature pages, YOLOv11 localizes signatures, ResNet-50 supplies deep features, and a dual-descriptor layer combines cosine similarity with an independent-minimum perceptual hash (dHash) to separate style consistency from image reproduction. Applied to 90,282 Taiwan audit reports (2013–2023), the pipeline yields 182,328 signatures from 758 CPAs; primary analyses are scoped to the Big-4 sub-corpus (437 CPAs; 150,442 signatures). Distributional diagnostics show that the apparent multimodality of the descriptor distribution dissolves under joint firm-mean centring and integer-tie jitter (p rises to 0.35), so no within-population bimodal antimode anchors the operational thresholds. We instead adopt an anchor-based inter-CPA coincidence-rate (ICCR) calibration at three units: per-comparison (0.0006 at cos$>0.95$; 0.0013 at dHash$\leq 5$; 0.00014 jointly), pool-normalised per-signature (0.11 under the deployed any-pair high-confidence rule), and per-document (0.34 for the operational HC+MC alarm). Firm heterogeneity is decisive: Firm A's per-document HC+MC alarm rate is 0.62 versus $0.09$–0.16 at Firms B/C/D after pool-size adjustment, and under the deployed any-pair rule $77$–99\% of inter-CPA collisions concentrate within the source firm — consistent with firm-level template-like reuse. We position the system as a specificity-proxy-anchored screening framework with human-in-the-loop review, not as a validated forensic detector; no calibrated error rates are reportable without signature-level ground truth.