Electronic Signatures in MES

An Electronic Signature (E-Signature) is the digital binding of a verified identity to a specific action or record. Within a Manufacturing Execution System (MES), it serves as a tamper-proof audit trail for approvals, quality checks, and process interventions, ensuring full compliance and traceability.

The 3 Pillars of a Compliant E-Signature

To meet international standards like FDA 21 CFR Part 11, a digital signature must capture:

1. Who: Clear identification of the person signing (Attributability).
2. When: A secure, synchronized, and non-alterable timestamp.
3. Meaning (Intent): The specific purpose of the signature (e.g., "Performed by", "Reviewed by", or "Approved").

Signature Types in the Factory Environment

1. Credential-based Signatures

The user re-authenticates by entering their password or using biometric ID before an action is recorded.

• Use Case: Standard for GxP and highly regulated manufacturing.
• Benefit: Ensures that the person at the terminal is truly the authorized user.

2. Digital / Certificate-based Signatures (PKI)

Uses cryptographic keys to lock a document or record.

• Use Case: Finalizing Electronic Batch Records (eBR) or compliance reports.
• Benefit: Provides maximum proof against tampering and ensures document integrity over time.

3. Simple Click-to-Confirm

A basic confirmation button without re-authentication.

• Risk: Usually insufficient for regulatory requirements. Only suitable for low-risk, non-quality-related tasks.

Critical MES Use Cases

• Line Clearance & Setup: Formally signing off that a line is ready for a new order.
• Overrides & Deviations: Mandatory signature plus a "Reason for Change" when bypassing standard limits.
• Quality Disposition: Signing off on "Go/No-Go" decisions for inspected lots.
• Review & Approval: Facilitating the "Four-Eyes Principle" where a supervisor must review an operator's entries.

Best Practices & Pitfalls

• Avoid Shared Logins: Every signature must be unique to an individual to maintain Data Integrity.
• Intent Matters: Always display the meaning of the signature (e.g., "By signing this, I confirm that the cleaning was performed according to SOP-01").
• Combat Signature Fatigue: Only enforce signatures at Critical-to-Quality points to ensure operators remain vigilant.