Once the sender obtains this link, they then send a message to the recipient via an existing pairwise session. This message contains a link to the content, a hash of the content, and the decryption key. The recipient then uses an onion request to pull the encrypted attachment from the centralised file server and decrypt it locally using the decryption key provided by the sender. The recipient also checks the hash against the attachment, ensuring the file has not been modified in transit.