Notes on CFD v4.0 and v3.3

These notes were written when v3.3 was introduced and superseded v3.2 in 2017. All these notes are equally valid for v4.0 (introduced 2021).

• The attribute names in v4.0/3.3 all begin with capital letters, so sello in v3.2 becomes Sello in v3.3. Be careful to change the attribute argument in any calls to GetXMLAttribute.

  FirmaSAT ATTRIBUTE -d -a sello -e Comprobante -i cfdv33-signed-tfd.xml
  Attribute=[sello] Element=[Comprobante]
  Error code -21: Match not found/No se pudo encontrar datos coincidente
  

  FirmaSAT ATTRIBUTE -d -a Sello -e Comprobante -i cfdv33-signed-tfd.xml
  Nm+AyKSlay8Lg5Z++uSHQNLC6FUGB9KInjk9cm0I+n4Jwxwp2SwdEaRP6hTH+f2veoqm6Z
  ...aFplBE3LQrPda+DjM2296Mje0mvoX+KtQpHAUOZoCg==
  

• The TimbreFiscalDigital element is required to be version 1.1 for CFD v4.0/3.3. The data for the QRcode image is different, too.
• The hash algorithm in a v4.0/3.3 signature is required to be SHA-256 (the signature algorithm is sha256WithRSAEncryption). In FirmaSAT, the hash algorithm used to form digests and signatures is chosen automatically depending on the type and version of the document detected.
• The NoCertificado node is now included in the pipe string (cadena original) and must be completed before computing the digest or signing the document. This must match the actual certificate used for signing. In v3.2 you could use 00000000000000000000 as a placeholder; this no longer applies with v4.0/3.3.
  • Use InsertCertificateDetails to insert the certificate details (NoCertificado and Certificado) before doing further work.
• The XSD validation of a v4.0/3.3 document refers to huge XSD catalog files. See Checks against XSD catalog files.
• FirmaSAT is designed to produce digital signatures and analyze XML documents for correct structure and missing attributes. It does not carry out any further checks such as those in the guidelines GuíaAnexo20.pdf (local copy, 3.6 MB, official link) or Guia_comple_pagos.pdf (local copy, 663 kB). You must carry out any other checks independently.