Table of Contents

Ubuntu - OpenSSL - Compute a checksum of a file

OpenSSL can compute a checksum (digest) against a file.

To ensure that the contents of a file has not been tampered with, OpenSSL can compute a unique checksum for the file.

Once this checksum is computed, it can be shared and, for example, anyone downloading the file can run the same checksum process to ensure that they get the same checksum - which ensures that the contents of a file have not changed.

Get a list of checksum methods that OpenSSL supports

openssl dgst -list

returns: 

Supported digests:
-blake2b512                -blake2s256                -md4                      
-md5                       -md5-sha1                  -ripemd                   
-ripemd160                 -rmd160                    -sha1                     
-sha224                    -sha256                    -sha3-224                 
-sha3-256                  -sha3-384                  -sha3-512                 
-sha384                    -sha512                    -sha512-224               
-sha512-256                -shake128                  -shake256                 
-sm3                       -ssl3-md5                  -ssl3-sha1                
-whirlpool

Compute an MD5 Checksum for a file

openssl dgst -md5 test.sh

returns: 

MD5(test.sh)= 68e2009b8a69745f4371011194a16116

NOTE: This can also be run as: 

openssl md5 test.sh

Compute an MD5 Checksum for all files in a directory

OpenSSL can also be combined with find to produce fingerprints for several files: 

find /home/peter -type f -print0 | xargs -0 openssl md5
 
or
 
find /home/peter -type f| xargs -d '\n' openssl md5

NOTE: The xargs command takes white space characters (tabs, spaces, new lines) as delimiters.

To accommodate for files which may contain spaces, the -d option is used to limit xarg delimiters to only the new line characters ('\n').