Certify

verb

1. To attest to (a fact) as the truth.
2. To authenticate or verify in writing.
3. To attest that a product, service, organization, or person has met an official standard.

   "These blankets have been certified as fireproof."

4. To inform; to tell (a person) that something is true.
5. To assure (oneself) of something; to ascertain.