Accreditation Decision: A formal statement by a designated accrediting authority (DAA) regarding acceptance of the risk associated with operating a DoD information system (IS) and expressed as an authorization to operate (ATO), interim ATO (IATO), interim authorization to test (IATT), or denial of ATO (DATO). The accreditation decision may be issued in hard copy with a traditional signature or issued electronically signed with a DoD public key infrastructure (PKI)-certified digital signature.