Sage-Tips

Should you compress before or after encryption?

You should compress before encrypting. Encryption turns your data into high-entropy data, usually indistinguishable from a random stream. Compression relies on patterns in order to gain any size reduction.

Does GPG compress by default?

By default GPG will compress the content of encrypted message, which contains a variable part in addition to the payload. Therefore the size of the encrypted message may vary even when the payload does not change.

Can you compress and encrypt at the same time?

So yes, you can compress encrypted files. But since encrypted data is very similar to random data, it doesn’t compress very well – so if you can, compress before encrypting. Otherwise the “compression” will be fairly useless.

Is GPG still secure?

GPG is very secure, as long as your passphrase is long and strong enough. In practice, your passphrase will almost always be the weakest link. This instructs GPG to use a password hashing method that is as slow as possible, to try to provide a bit of extra resistance against password guessing attacks.

Should all data be compressed?

It is better to compress before encrypting. Any proven block cipher will reduce the data to a pseudo-random sequence of bytes that will typically yield little to no compression gain at all.

Why compression is done before encryption and not the opposite?

Compression uses patterns in data to shorten the size of the data, saving bandwidth and storage space in the process. Compression is not complicated to reverse so retrieving the original would be easy. This is why many people use encryption and compression together when sending messages.

Does PGP encryption reduce size?

3 Answers. Most likely, the encrypted file is base64 encoded which would account for 33.3\% file increase (you encode three bytes of data in four bytes of base64 data). Inserting a new line every 64 characters to make it easier to read (as is done by ASCII armor in openssl, GPG, PGP) will increase the size by 65/64.

Does PGP encryption compress files?

PGP is a hybrid cryptosystem. When a user encrypts plaintext with PGP, PGP first compresses the plaintext. Data compression saves modem transmission time and disk space and, more importantly, strengthens cryptographic security.

When using compression and encryption together which is the correct order of operations?

This is why, when we have to perform both compression and encryption, we will always compress first and then encrypt, as shown in the workflow of Figure 1. Encryption after compression.

Should you encrypt data at rest?

First and foremost, encrypting data at rest protects the organization from the physical theft of the file system storage devices (which is why end-user mobile devices from laptops to cell phones should always be encrypted). Encrypting the storage subsystem can protect against such attacks.

Can GPG encryption be broken?

As long as you use strong keys and and encrypt/hide your private keys (2 layers of 2048 bit encryption minimum), GPG is nearly unbreakable.

Are GPG keys secure?

To help safeguard your key, GnuPG does not store your raw private key on disk. Instead it encrypts it using a symmetric encryption algorithm. That is why you need a passphrase to access the key.

Should I compress my files before or after encryption?

If you compress after encryption and the compression does any good (i.e. it really reduces the length by a non-negligible amount) then you can ditch the encryption, it is awfully weak. Encrypted text ought to be indistinguishable from randomness; even badly encrypted data cannot usually be compressed. Therefore, compress before encryption.

How do I decrypt a file without the GPG suffix?

You will be prompted for the passphrase that you used to encrypt the file. If you don’t use the –output option, the command output goes to STDOUT. If you don’t use any flags, it will decrypt to a file without the .gpg suffix.

Why doesn’t compression reduce the size of encrypted data?

Since encryption destroys such patterns, the compression algorithm would be unable to give you much (if any) reduction in size if you apply it to encrypted data.

How do I add cipher-Algo AES256 to my GPG file?

If you choose not to add the cipher-algo AES256 to your gpg.conf file, you can add –cipher-algo AES256 on any of these simple example command lines to override the default cipher, CAST5. Both commands below are identical. They encrypt the test.out file and produce the encrypted version in the test.gpg file: