A government login screen can feel small, but it holds big keys.
Key Takeaways
The page in one glance
- This article is about the taxpayer-linking page on seafi.campeche.gob.mx, used in Campeche, Mexico (North America).
- The screen asks for a key file, a certificate file, and a password tied to that key.
- A short security message on the page says the data is protected with end-to-end encryption.
- Most problems come from mismatched files, the wrong password, or the wrong file format.
Story & Details
A screen that asks for three things
In January two thousand twenty-six, the SEAFI Campeche site points people toward online tax services, including the SIAF portal for declarations and payments in Campeche, Mexico (North America). The linking step is strict and quiet. It does not ask for a long story. It asks for three items: a key file, a certificate file, and the password that unlocks the key.
The labels are blunt. The first field is for the key. The second is for the certificate. The third is for the password. One button waits at the bottom. The design suggests a clear idea: prove control of a private key, and the system can link an account.
What those files really are
A certificate file with the ending .cer is the public face. It is meant to be shared with systems that need to verify a signature. A key file with the ending .key is the private half. It is meant to stay secret. The password does not belong to a general tax website login. It belongs to the private key file itself.
That split is not just paperwork. It is basic cryptography. A private key creates a signature. A public certificate helps check it. If the private key is missing, the signature cannot be created. If the password is wrong, the key stays locked. Official SAT guidance also stresses a core point: the authority does not store the private key file, and it does not know its password. It can only help recover the public certificate, because the certificate is public.
Why the security line matters, and what it does not prove
The page says the information is protected with end-to-end encryption, and that neither the finance authority nor outside parties can read it. This line is meant to build confidence at the exact moment the most sensitive item is typed: the private-key password.
Still, real safety also depends on simple habits. A private key should not be copied into random chats or shared drives. It should not be left inside a forgotten compressed folder on a shared device. A certificate can travel more freely, but the key should travel carefully.
When it fails, the failure is usually simple
Many errors are not mysterious. They are mismatches. A key file and a certificate file must belong together. When they do not, the system can reject the attempt even if both files look correct.
Other failures come from packaging. Some people have a combined file such as .p12 or .pfx, while the portal expects separate .key and .cer files. The data may be there, but the container is not what the portal accepts. On phones, there is also a basic friction: the browser may not open the file picker, or it may not see the folder where the files are saved.
A tiny Dutch phrase guide
Dutch is spoken in the Netherlands (Europe), and short phrases can be useful when dealing with files and passwords.
The first sentence is used when a password is lost and help is needed:
Ik ben mijn wachtwoord vergeten.
A simple meaning is: a lost-password message. Word by word, ik means I, ben means am, mijn means my, wachtwoord means password, vergeten means forgotten. The tone is neutral and safe for most situations.
The second sentence is used when looking for an official download page:
Waar kan ik mijn certificaat downloaden?
A simple meaning is: a question about downloading a certificate. Word by word, waar means where, kan means can, ik means I, mijn means my, certificaat means certificate, downloaden means download. The tone is neutral; adding alstublieft can make it more polite in everyday speech.
Conclusions
Small fields, serious meaning
A key file, a certificate file, and a password can look like routine inputs. They are not. They are a compact test of identity, built on a public certificate and a private key that should stay private. Once that idea clicks, the screen becomes easier to read, and the common errors become easier to spot.
Selected References
[1] https://seafi.campeche.gob.mx/
[2] https://miportal-siaf.seafi.campeche.gob.mx/assets/docs/Gu%C3%ADa_Declaraciones_y_Pagos_de_Impuestos_Portal_SIAF.pdf
[3] https://wwwmat.sat.gob.mx/aplicacion/44275/descarga-de-manera-directa-tu-certificado-de-e.firma
[4] https://support.docusign.com/s/document-item?language=en_US&_LANG=enus&bundleId=yca1573855023892&topicId=ava1696596479046.1.html
[5] https://www.ventanillaunica.gob.mx/cs/groups/public/documents/contenidovu/mdaw/mda3/~edisp/vucem008380.pdf
[6] https://www.youtube.com/watch?v=LWOmgViWhKk
Appendix
Certificate: A digital file that carries public information used to verify a signature; in this topic it is often the file ending in .cer.
Digital signature: A mathematical proof created with a private key that can be checked with a matching public certificate.
End-to-end encryption: A security design where data is encrypted so that only the intended endpoints can read it, not intermediaries.
Key file: A private cryptographic file, often ending in .key, used to create signatures and meant to remain secret.
Password: The secret text that unlocks the private key file; it is different from a general website login password.
Public certificate: The shareable side of a signing setup, used for verification rather than signing.
Taxpayer linking: The act of connecting an online account to a tax identity by proving control of required credentials.
My Diary - Leonardo Cardillo 