Am i able to use client's certificate in iPhone

I'm iphone developer and have a client. One day he wants to update uploaded live app in App Store and give me source code, his apple id and password. I entered iOS Provisioning Portal by using his apple id. there was already one distribution certificate and i downloa开发者_JAVA技巧ded it (distribution_identity.cer) and provisioning file (xxx.mobileprovision). I setup provisioning file, but i got a error "iPhone App Signing: A valid signing identity matching this profile could not be found in your keychain". so I setup distribution_identity.cer file but still got the error. I think I need the p12 file for distribution certificate. can i make the p12 file? or do I need the p12 file to client? I'm not working out a solution.

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you need the .pi2 file from the client.

The other method is , revoke the certificate from the portal and regenerate it from scratch.

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You need the p12, and you might also want to create a separate User account on your Mac for using it so that the XCode doesn't get confused by having multiple Developer certificates in the current account's Keychain.