“The NSA published a document on its website titled 'Communications with Extraterrestrial Intelligence' in its declassified documents section under Cryptologic Spectrum.”

The NSA does host a document titled 'Communications with Extraterrestrial Intelligence' by NSA cryptologist Lambros D. Callimahos in its declassified archives, and its connection to Cryptologic Spectrum is corroborated by multiple sources including a 2006 Schneier on Security post. The document is an academic/theoretical piece on cryptology and SETI — not a disclosure of actual alien contact. Multiple independent sources confirm it's findable directly on nsa.gov with DOCID: 3052333.