When compressing and encrypting, should I compress first, or encrypt first?

encryption compression performance aes zlib
seisatsu picture seisatsu · Jan 13, 2011 · Viewed 36.9k times · Source

If I were to AES-encrypt a file, and then ZLIB-compress it, would the compression be less efficient than if I first compressed and then encrypted?

In other words, should I compress first or encrypt first, or does it matter?

Answer

Ferruccio picture Ferruccio · Jan 13, 2011

Compress first. Once you encrypt the file you will generate a stream of random data, which will be not be compressible. The compression process depends on finding compressible patterns in the data.

Related questions

Does AES (128 or 256) encryption expand the data? If so, by how much?

I would like to add AES encryption to a software product, but am concerned by increasing the size of the data. I am guessing that the data does increase in size, and then I'll have to add a compression algorithm …

Read More
Encrypt and decrypt a string in C#?

How can I encrypt and decrypt a string in C#?

Read More
Encrypting & Decrypting a String in C#

What is the most modern (best) way of satisfying the following in C#? string encryptedString = SomeStaticClass.Encrypt(sourceString); string decryptedString = SomeStaticClass.Decrypt(encryptedString); BUT with a minimum of fuss involving salts, keys, mucking about with byte[], etc. Been Googling and …

Read More