Next, extract your public key and send it to the person that will be encrypting data to send to you:. Where -encrypt means encrypt, -in dt. Where -decrypt means decrypt, -in dt. When using the following commands, you will be prompted for the password shared secret key. The shared key can live in a protected file -kfile , or share by word of mouth. Remember, the encrypted file is only as safe as the secret is truly secret. While not used in the provided examples, -salt is recommended and will protect against dictionary attacks.
Where enc means encrypt, -aes is the cipher defaults to -aescbc , -base64 encoded, -in dt. Where enc -d means decrypt, -aes is the cipher make sure to use the same cipher as used when encrypting , -base64 if encoded, -in dt. As you noticed in the previous example without pbkdf2, the key derivation was deprecated and it recommends to use -pbkdf2 for key derivation. Note that the only difference when using pbkdf2 is the corresponding flag.
Other flags stay the same. The default number of PBKDF2 iterations is 10,, but this can be changed to a higher number using the -iter flag. For example, the 1Password service derives keys with , iterations. To decrypt the pbkdf2 encrypted data if using iterations other than the default make sure to include that with -iter :. Only use this if you need to send data in the form of text format via email etc.
You always want to use a salt while encrypting. This parameter is actually redundant because a salt is used whether you use this or not which is why it was not used in the "Short Answer" above! If only the key is specified, the IV must additionally be specified using the -iv option. When both a key and a password are specified, the key given with the -K option will be used and the IV generated from the password will be taken.
It probably does not make much sense to specify both key and password. When only the key is specified using the -K option, the IV must explicitly be defined.
When a password is being specified using one of the other options, the IV is generated from this password. The default algorithm as of this writing is sha But this has changed over time. It was md5 in the past. So you might want to specify this parameter every time to alleviate problems when moving your encrypted data from one system to another or when updating openssl to a newer version. I find it incredible that OpenSSL uses such a weak password derived hash for the key!
Be sure to use the "-md md5" option for compatibility with files that were encrypted on older openssl without the -md option specified, otherwise you will find that files won't decrypt on newer systems: github. Default values change between versions of openssl. Version 1. It looks like the password is stored for some period of time, which I don't want.
I think you have gpg-agent running — moo. Encrypt: openssl enc -in infile. Andrii Abramov 8, 8 8 gold badges 62 62 silver badges 85 85 bronze badges. Ken Cheung Ken Cheung 1, 14 14 silver badges 13 13 bronze badges. Related to jonasl's comment, note that -k symmetrickey is misleading. The -k option is used for specifying a password, from which OpenSSL derives the symmetric key. If you want to specify the symmetric key, you must use the -K option. Currently the accepted answer makes use of it and it's no longer recommended and secure.
It is very feasible for an attacker to simply brute force the key. Do this: openssl enc -aescbc -pbkdf2 -iter -in hello -out hello. Read the damn question. Arnold Balliu Arnold Balliu 1, 9 9 silver badges 20 20 bronze badges.
However the iteration count is extrememly low, and needs to be set to a much higher level. If that count is randomised, then you also get a extra level of 'saltiness' to your encryption.
To encrypt a file: openssl aescbc -e -salt -pbkdf2 -iter -in plaintextfilename -out encryptedfilename To decrypt a file: openssl aescbc -d -salt -pbkdf2 -iter -in encryptedfilename -out plaintextfilename. Uwe Keim Which as these options keep changing, means you need to also keep a record of what options was used when creating each openssl encrypted file.
Especially as the iteration count should increase with time! For one solution see as relatively simple wrapper around openssl enc Also see github. Update using a random generated public key.
Ewoks However its default iteration count is very low, and needs to be much larger. Source file: openssl-pkcs Found a problem? See the FAQ. By default a PKCS 12 file is parsed. A PKCS 12 file can be created by using the -export option see below. Standard input is used by default. They are all written in PEM format. Otherwise, -password is equivalent to -passin. Cannot be used in combination with the options -password, -passin if importing or -passout if exporting.
Standard output is used by default. They must all be in PEM format. The order doesn't matter but one private key and its corresponding certificate should be present. If additional certificates are present they will also be included in the PKCS 12 file. If not present then a private key must be present in the input file.
If no engine is used, the argument is taken as a file; if an engine is specified, the argument is given to the engine as a key identifier. This name is typically displayed in list boxes by software importing the file.
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