Contact your intended conversation partner via some other authenticated channel, such as OpenPGP-signed email or over the phone. You should tell each other your fingerprints. (A fingerprint is a checksum that identifies an encryption key.) If the fingerprint matches, you should indicate in the dialog below that you have verified the fingerprint.
Jarri harremanean zure elkarrizketa lagunaz beste bide autentifikatu batetik, adibidez, OpenPGP sinadurazko postaz edo telefonoz.  Besteei zure hatz-marka erakutsi behar diezu. (Hatz-marka bat, kontroleko batura bat da, zure enkriptatze gakoa identifikatzen duena.) Hatz-marka bat badator, azpiko elkarrizketan hatz-marka egiaztatu duzula adierazi beharko zenuke.