http://www.bakernet.com/NR/rdonlyres/AF9A22AD-DD24-4E5C-BB1B...


a) Advanced electronic signature is the signature enabling
identification of the signer, exclusively linking him to the
accompanying digital document or associating and enabling the
detection of any further modification thereto.
An advanced digital signature covered by a current certificate will
have the same legal effect and evidentiary value as hand-signed
documents.
b) Digital document is any data message containing
information or writing generated, sent, received or stored in
electronic or optic media or any other technology.
c) Digital certificate is a certificate issued by the SAT or by a
certification service provider, enabling the linkage of the holder’s
identity with a public code. The certificates will have two-year
effective periods, upon the expiration of which a new certificate
may be requested.
d) Digital stamp is understood to be the confirmation receipt
issued by the tax authorities, evidencing that a digital document
was received by the corresponding authority. Absent proof to the
contrary, the date and time the document was received are
presumed to be those on the stamp.
In these terms, digital documents bearing advanced
electronicsignatures are covered by the author’s digital
certificate, enabling the verification of the authorship and
integrity of the document through the remission to the original,
using the public code.
It should be noted that during 2004 the use of the advanced
electronic signature will be optional for taxpayers, and until such
signature is obtained they should continue to use the electronic
signatures they have been using with the SAT, unless the
authority approves other electronic return and audit filing media
through general rules. The electronic signatures currently used
are known as the Confidential Electronic Identification Code for
Payments via Internet.
Requirements for Obtaining a Digital Certificate
Individuals. Individuals must process their digital certificates
with the SAT or with a certification service provider authorized
by the Bank of Mexico, our central bank. Government employees
should process their certificates with the Ministry of Public
Functions.
fiscales obliguen a la presentación de documentos, éstos deberán
ser digitales y contener una firma electrónica avanzada del autor,
salvo que se prevea algún otro mecanismo para su presentación.
Para la mejor comprensión del alcance del presente capítulo,
consideramos oportuno hacer una breve definición de los
conceptos incorporados al CFF:


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Note added at 1 hora (2010-05-20 15:34:38 GMT)
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Gracias Neil. Además creo que es una fuente muy fiable por venir de Baker & McKenzie (Mexico) que es uno de los más prestigiosos despachos de abogados. Por mis muchos años de experiencia en banca y por haber trabajo personalmente con ellos, me fio bastante de ellos.

Saludos,