0

I have encrypted a file with the same command line with two different openssl versions: 1.0.1t and 1.1.0e. Then I try to decode both with version 1.0.1t and I cannot decode the latter.

Can you please tell me why and where am I wrong? How can I encrypt and safely decrypt without changing the command line: openssl enc -d -a -bf -in <infile> -out <outfile> -pass pass:<password>?

If you would like to answer on more question: how can I make the cipher more resilient?

Here's how to reproduce the situation. On the host with openssl 1.0.1t:

user@101t$ openssl version OpenSSL 1.0.1t 3 May 2016 user@101t$ echo "pippo" > prova user@101t$ openssl enc -e -a -salt -bf -in "prova" -out "prova1.enc" -pass pass:pippo

On the host with openssl 1.1.0e:

user@110e$ openssl version OpenSSL 1.1.0e 16 Feb 2017 user@110e$ echo "pippo" > prova user@110e$ openssl enc -e -a -salt -bf -in "prova" -out "prova2.enc" -pass pass:pippo

Copy prova1.enc to the host with openssl 1.0.1t and then into it type:

user@101t$ openssl enc -d -a -bf -in prova1.enc -out x -pass pass:pippo user@101t$ openssl enc -d -a -bf -in prova2.enc -out x -pass pass:pippo bad decrypt 139637189576336:error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt:evp_enc.c:516:

Thanks in advance

0

The default digest used for generating the key from the password changed in OpenSSL 1.1.0. In versions prior to that md5 was used - which is now considered insecure. In OpenSSL 1.1.0 the default digest is sha256.

In order to decrypt a file in OpenSSL 1.0.1t generated by OpenSSL 1.1.0 you should add "-md sha256" to your command line arguments. If that is not possible then you can also force OpenSSL 1.1.0 to use md5 as its digest by adding "-md md5" to the encryption command line arguments. This is obviously insecure but should work.

  • Thanks a lot! Just a note: before posting the issue I have tried to change the digests config parameter in openssl.cnf to digests = md5, sha1 but it didn't solve the problem. Is it possible to set md5 as default without specifying it as a command line argument? – fero May 23 '17 at 15:14
  • No, unfortunately that isn't possible. The "enc" application only reads the digest from the command line args and not from the config file. Please could you mark my answer as correct if it addresses your issue? – Matt Caswell May 23 '17 at 22:06
  • -1 for suggesting that SHA-256 is secure for this use. – AndrolGenhald Apr 18 at 17:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.