Security is central to a signing platform. Below is how SignMyLetters protects your data in transit, at rest, and throughout the signing lifecycle. We take a defense-in-depth approach and continually improve our controls.
Encryption in transit
All traffic to and from the Service is encrypted with TLS (HTTPS). Certificates are automatically issued and renewed, so connections to signmyletters.com and its APIs are always encrypted.
Encryption at rest
Sensitive data is encrypted at rest using AES-256-GCM, including:
- uploaded government-issued identity documents;
- drawn and uploaded signature images;
- business identifiers such as EINs;
- configured integration secrets (e.g. email and payment credentials).
The master encryption key is held in the runtime environment — never in the database it protects — so encrypted records are useless without it.
Passwords
Account passwords are never stored in plaintext. They are hashed with argon2id, a modern, memory-hard algorithm designed to resist brute-force and GPU attacks.
Cryptographic signatures (PAdES)
Documents marked secure receive an embedded PAdES digital signature (PKCS#7 / X.509) applied to the final PDF. This provides integrity and non-repudiation: any change to the document after sealing invalidates the signature.
Tamper-evident audit trail
Every meaningful action — created, sent, viewed, signed, completed — is recorded in a hash-chained audit log, where each entry cryptographically links to the previous one. Reordering, removing, or altering any entry breaks the chain, so the record is verifiably intact. A summary audit page is included with each completed document.
Access control
Access is governed by role-based access control (super-admin, business owner, signer, and others) with least-privilege enforcement. Signing links are single-use per signer and scoped to only the fields assigned to that signer. Disabled accounts cannot authenticate.
Object storage & access
Documents and assets are stored in dedicated object storage and served to browsers through short-lived, signed URLs rather than public links.
Infrastructure
The platform runs as isolated, containerized services (application, database, cache, and object storage) behind a hardened reverse proxy. Internal services are not exposed to the public internet; only encrypted web and API endpoints are reachable.
Responsible disclosure
Found a vulnerability? Email security@signmyletters.com
We appreciate coordinated disclosure. Please give us a reasonable opportunity to investigate and remediate before any public disclosure, and avoid accessing or modifying other users' data.
Questions
For security or privacy questions, see our Privacy Policy or contact us.