encryption/decryption with multiple keys

Question

Is it possible to encrypt data, such that it can be decrypted with several different keys?

Example:

I\'ve encrypted data with key1, but I want

Answer 1

Yes it's possible

Yes encryption for multiple recipients is possible. Also it seems logical when you think that you might want to be able to read what you've sent to someone and to do so you need to be in the recipients list.

Command line

Here is how to do it through gpg command line (as described in David Segonds' answer):

gpg --encrypt \
  --recipient alice@example.com \
  --recipient bob@example.com \
clear-message.txt

GUI client

Your GUI must provide a way to encrypt for several people

Mechanism

There is a question on Information Security, GPG File size with multiple recipients?, that explain the encryption mechanism:

GPG encrypts the file once with a symmetric key, then places a header identifying the target keypair and an encrypted version of the symmetric key.

[...] When encrypted to multiple recipients, this header is placed multiple times providing a uniquely encrypted version of the same symmetric key for each recipient.