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System: Linux Mint 18.3 Cinnamon 64-bit.

OpenSSL: 1.0.2g

Ordinarily, I would encrypt a file as follows:

openssl enc -aes-256-cbc -salt -in somefile -out somefile.enc

But I wonder what algorithm will be used to hash my password and if I can change it?

Vlastimil Burián
  • 4,376

1 Answers1

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I found out by accident, here, that for openssl version 1.1.0:

-md digest
    Use the specified digest to create the key from the passphrase. The default algorithm is sha-256.

So, there is no point of specifying the message digest algorithm for the newer version of openssl as it already uses SHA-256.

But since on my system there is openssl version 1.0.2g, I dug further and found out, here, that:

... In OpenSSL 1.1.0 we changed from MD5 to SHA-256 ...

Essentially, this means, my openssl will by default use the old and obsolete MD5.

Luckily, this can be changed to SHA-256 with openssl version 1.0.2g:

openssl enc -aes-256-cbc -md sha256 -salt -in somefile -out somefile.enc

If you have an older openssl version than me, you might want to try -md sha1, if the above fails.

Vlastimil Burián
  • 4,376