Selectively obfuscating, or obscuring, a portion or portions of information in a multi-party transmission. A user participating in a multi-party exchange signals a communication device (or proxy) that he will provide private information that is to be perceptible only to a subset of the other participants. This user also identifies that subset, preferably by providing a group identifier for a group in which that subset of participants are members. The communication device transmits a member-specific descriptor comprising an encrypted version of a group key, and uses this group key to encrypt the private information that is to be perceptible only to the subset. Device-specific characteristics of participant devices are used, in addition to user-provided data (such as a user's log-on identifier and/or password), as input to create cryptographic key information. Only participants in the subset can decrypt the encrypted private information; other participants preferably receive a filler pattern instead.