Security

How I handle your credentials

Your e.firma, digital seal certificates (CSD) and payment keys stay in your infrastructure. I work with the least access the job needs, everything I do is logged in your systems, and my access ends when the project does.

e.firma (FIEL)

  • Integrating payments or issuing CFDI doesn't need your e.firma, so I don't ask for it.
  • The one feature that does, SAT Descarga Masiva (bulk CFDI download), gets it from your secret manager (AWS Secrets Manager, Google Secret Manager or Azure Key Vault) at runtime. I write the code that reads it; your team loads the .cer, .key and password.
  • I never receive e.firma files or passwords by email, chat or shared drives.

Digital seal certificates (CSD)

  • Development and testing use SAT's public test certificates, never yours.
  • Your production CSD is uploaded by your team to your PAC or to your own secret store.

Payment keys (Stripe, Mercado Pago, Conekta, Clip)

  • I build and test in sandbox or test mode.
  • Where the provider supports it, production uses restricted keys limited to the permissions the integration needs.
  • Your team sets production keys and webhook secrets as environment variables or secrets in your infrastructure. They're never committed to a repository.

Access to your systems

  • A named account for me in your cloud, repositories and tools, with two-factor authentication. No shared passwords.
  • Least privilege: only the services and environments the project touches. Production access only when a task needs it.
  • What I do is recorded in your own audit logs (for example AWS CloudTrail, Google Cloud Audit Logs or your Git history).
  • Code lives in your repositories from the first commit.

Your data

  • Production data stays in your systems. I work with test or anonymized data wherever possible.
  • No customer data, RFCs or invoices go into AI tools without your written approval, and when they do, personal data is redacted first.

Paperwork and the end of a project

  • I sign an NDA before getting any access.
  • The contract states what I'm responsible for. I'm an engineer, not your contador: your contador signs off on the fiscal rules the system applies.
  • At the end of the project, my access is removed and we go through a key-rotation checklist together, so nothing I could have seen stays valid.

Questions

If your security or compliance team needs something specific, such as a questionnaire, a particular secret store or a specific approval flow, email me (hola@cesarayala.dev) and we'll work to your process. For how this website handles visitor data, see the privacy notice.