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Coldcard / Public disclosure

Delta PIN private-key recovery

Researcher reported private-key recovery from the Delta PIN signing behavior.

Source date: 2025-09-30Reviewed: 11 October 2026

Affected scope

Delta PIN signing; full affected matrix unspecified

What the attack requires

Access to two affected transaction signatures.

Response & remediation

What changed

Vendor lists 5.4.4 and 1.3.4Q.

What this finding establishes

Feature-specific issue; do not describe all ordinary signatures as vulnerable.