How sharing and security go together ?
Very good question.
Giving the contents of your secret information to anybody may be considered at best unwise.
That is why you only mark a cpCard as shared with a particular user that is on your Friends list.
Your friend has to know the password/cypher you used to encode the cpCard with and get a .cpc file that contains the part of content that is necessary to decode it.
You will find .cpc files for your cpCards in your <UsersDirectory>/cpVault/<your_login>/ folder on your device.
Please do not modify their names as any modification will result in making them impossible to decipher.
It is generally smart to make backup copies of them from time to time but for sharing you have to find a file corresponding to a cpCard you're sharing and send it to your friend or give it to your friend on a PenDrive or any other medium of your choosing. The second option being the most secure.
Remember that .cpc file alone and password is not enough to decode the cpCard. Such a cpCard has to be marked as shared with a particular account.
There are four importand things to remember while sharing.
1. If you receive a .cpc file from your friend, put it in your <UsersDirectory>/cpVault/<your_login>/shares/ folder.
2. You have complete control of whom you share your cpCards with.
3. Even if you have given your .cpc file and password to your "friend" and changed your mind immediately afterwords you can just go to "shares' screen and remove the share. Your friend will not be able to decode your cpCard if you do this.
4. When you modify a cpCard you have to resend or "regive" the .cpc file to your friend for him or her to access the new version of the cpCard again. (provided you used the same password, if used a different one you have to update your friend about it as well)