Question 164. What is X.435?

ITU-T Recommendation X.435 [CCI91] and its equivalent F.435 are X.400-based standards (see Question 163) designed to support electronic data interchange (EDI) messaging. EDI needs more stringent security than typical e-mail because of its business nature: not only does an EDI message need protection against fraudulent or accidental modification in transit, but it also needs to be immune to repudiation after it has been sent and received.

In support of these security requirements, X.435 defines, in addition to normal EDI messages, a set of EDI "notifications." Positive notification implies that the recipient has received the document and accepts the responsibility for it; negative notification means that the recipient refused to accept the document due to a specified reason; and forwarding notification means that the document had been forwarded to another recipient. Together, these notifications form the basis for a system that can provide security controls comparable to those in the paper-based system that EDI replaces.