Re: Mass Effect 1 (PS 3)

The ability to open an encrypted container doesn't depend on the decryption skill of a single character. Instead, the decryption skills of all present characters are added up. For instance, if Shepard has 0 decryption, Tali has 7 decryption, and Garrus has 4 decryption, you will have a score of 11.

So if Shepard doesn't have decrypt skills, bring characters with a lot of decryption skill and you'll be able to open more containers.

The 'disc like item' you describe is from a combat skill, not decryption.