$ ledger --version
Ledger 3.3.2-20230330, the command-line accounting tool
with support for gpg encrypted journals and without Python support

Copyright (c) 2003-2023, John Wiegley.  All rights reserved.

This program is made available under the terms of the BSD Public License.
See LICENSE file included with the distribution for details and disclaimer.

and check for “with support for gpg encrypted journals”.

If it’s present, then all you have to do is encrypt your journal files and ledger will transparently decrypt the data as it reads. Doing this is a simple matter of encrypting the files with yourself as the recipient. If you only use gpg --encrypt to encrypt files for yourself (and not to send to other people) then the easiest way might be to configure GnuPG to encrypt with your own key by default:

$ echo default-recipient-self >> ~/.gnupg/gpg.conf

Alternatively, you can remember to pass the --recipient argument specifying the key ID or email address for your own key when you run gpg --encrypt.

Now you can just create some encrypted journal files:

$ cat 2024.journal | gpg --encrypt --armor > 2024.journal.gpg
$ ledger -f 2024.journal.gpg bal
        AUD 2,187.50  Assets
        AUD 2,150.00    Bank
           AUD 37.50    Cash
           AUD 12.50  Expenses:Food:Dining
       AUD -2,200.00  Income:Gifts
--------------------
                   0

For the sake of convenience, I give the encrypted files an extension like .asc or .gpg so that tools like vim-gnupg can transparently decrypt them for editing.

Ledger handles encryption transparently at the file-access level, so you can split up your configuration and journal postings into different files and make each encrypted or unencrypted as you like. Personally, I like to have a single plain-text file that defines my chart of accounts and then includes encrypted journal files containing the actual posting.