удостоверявам meaning in English

assure [assured, assuring, assures]▼(to give someone confidence in the trustworthiness of something)
verb
[UK: ə.ˈʃɔː(r)] [US: ə.ˈʃʊr]

attest [attested, attesting, attests]▼(to affirm to be correct, true, or genuine)
verb
[UK: ə.ˈtest] [US: ə.ˈtest]

authenticate [authenticated, authenticating, authenticates]▼(to render authentic)
verb
[UK: ɔː.ˈθen.tɪk.eɪt] [US: ɒ.ˈθen.təˌket]

certify [certified, certifying, certifies]▼(to attest as to)
verb
[UK: ˈsɜː.tɪ.faɪ] [US: ˈsɝː.tə.ˌfaɪ]

verify [verified, verifying, verifies]▼(law: to affirm something formally, under oath)
verb
[UK: ˈve.rɪ.faɪ] [US: ˈve.rə.ˌfaɪ]