encryption - GnuPG: How to encrypt/decrypt files using a certain key? -

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long story short, question is: how can force gnupg private/public key use when encrypting/decrypting files?

some explanation / long story

i have application must encrypt files before sending them s3.

users can download files using browsers website, in case must first decrypt files before serving them.

client side (delphi 2010): i'm going opt openpgpblackbox

server side (php 5), need figure out how encrypt/decrypt files non-interactive commands.

i installed gnupg on server, tried code:

clear_file='/full/path/my-file.zip' encrypted_file='/full/path/my-file.zip.pgp'  # encrypt file /usr/bin/gpg2 --encrypt "$clear_file"  # decrypt file /usr/bin/gpg2 --decrypt "$encrypted_file"

but seems can't specify, in commandline, keys use.

each user have own public/private key, need able specify key use encrypt/decrypt file in question.

my question is: how can force gnupg private/public key use when encrypting/decrypting files?

the options looking are:

--default-key $name$           use $name$ default key sign with. if option not used, default key           first key found in secret keyring.  note -u or --local-user overrides            option. --local-user $name$    -u     use  $name$    key  sign with. note option overrides --default-key.

or possibly:

--recipient $name$    -r     encrypt user id $name$. if option or --hidden-recipient not specified,            gnupg asks  user-id unless --default-recipient given. --default-recipient $name$           use  $name$  default recipient if option --recipient not used , don't ask if              valid  one. $name$ must non-empty.

these can used specify intended recipient, e.g. public key use signing/encryption. when decrypting files gnupg automatically selects correct key if exists in current keyring, can selected --keyring option, if multiple exist. gnupg can configured fetch necessary keys keyserver if available there.

you might interested in option --batch makes sure no interactive questions asked during excecution.

i suggest read through gnupg man page. there lot of options might useful , then.


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