attest vs vouch

attest and vouch both are verbs.

Word	Noun	Adjective	Verb	Adverb
attest	No	No	Yes	No
vouch	No	No	Yes	No

As verbs, vouch is a hyponym of attest; that is, vouch is a word with a more specific, narrower meaning than attest:

attest (verb)	vouch (verb)
authenticate, affirm to be true, genuine, or correct, as in an official capacity	give supporting evidence
provide evidence for; stand as proof of; show by one's behavior, attitude, or external attributes	summon (a vouchee) into court to warrant or defend a title
give testimony in a court of law	give personal assurance; guarantee
establish or verify the usage of	give surety or assume responsibility