For one user I generated a gpg2 key-pair. I exported these to ascii-armour text files as master.asc and pub.asc. Then took only the pub.asc onto the keyring of a second user on the same partition. I "signed" a simple text file (say trial.txt) with the master key and also transferred it to the home directory of the second user. The pub key on the second user's keyring could verify the signature on the signed text file (trial.txt.gpg) but could not decrypt it. Also, a file encrypted by the second user with the pubkey could be decrypted by the masterkey. Each key therefore has, embedded in its structure, information about child/parent keys. Can anyone thrown light on the actual method of incorporation of this mutual recognition in the key structures? Note:The same kind of recognition happens with sub-keys derived from the Master-key. Can't find any literature which details. Help pl.