Encryption and Decryption in Linux - I

Encryption:
          Nothing but the conversion of plain text to cipher text(not understandable).

Decryption:
         It's conversion of  cipher text to plain text.

There are wide variety of tools to achieve it.This post deal with rapid fire commands that you can throw at terminal

Tools used:
       [+] Openssl
       [+] tr
       [+] base64

Mostly the above tools are preinstalled in lot of distribution if not download it from software repository

Let's get started

{1} BASE64 encryption and decryption
 
Most widely used algorithm for simple encryption and decryption for conversion of binary data into ASCII format ( Used in MIME for conversion of Non-ASCII to ASCII characters ) More details click the above link.

To convert binary to ASCII uses below commands

              echo "Sample text" | base64
              
                 U2FtcGxlIHRleHQK

To decrypt use

                echo "U2FtcGxlIHRleHQK" | base64 -d

                Sample text

Note:
          -d    => Decoding flag

{2} ROT13 encryption and decryption

One of the famous algorithm which can be used for simple encryption and decryption.sweet thing about this algorithm is both encryption and decryption use same code.

     One Liner to encode/decode text


       > echo "Sample text" | tr 'A-Za-z' 'N-ZA-Mn-za-m'   
           Fnzcyr grkg

       > echo "Fnzcyr grkg" | tr 'A-Za-z' 'N-ZA-Mn-za-m'
          Sample text


{3}Openssl encryption and decryption


OpenSSL is a cryptography toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1)
       network protocols and related cryptography standards required by them.

       The openssl program is a command line tool for using the various cryptography functions of OpenSSL's crypto library from the
       shell.  It can be used for

        o  Creation and management of private keys, public keys and parameters
        o  Public key cryptographic operations
        o  Creation of X.509 certificates, CSRs and CRLs
        o  Calculation of Message Digests
        o  Encryption and Decryption with Ciphers
        o  SSL/TLS Client and Server Tests
        o  Handling of S/MIME signed or encrypted mail
        o  Time Stamp requests, generation and verification

Algorithms in Openssl

   MESSAGE DIGEST COMMANDS
       md2       MD2 Digest

       md5       MD5 Digest

       mdc2      MDC2 Digest

       rmd160    RMD-160 Digest

       sha       SHA Digest

       sha1      SHA-1 Digest

       sha224    SHA-224 Digest

       sha256    SHA-256 Digest

       sha384    SHA-384 Digest

       sha512    SHA-512 Digest

   ENCODING AND CIPHER COMMANDS
       base64    Base64 Encoding

       bf bf-cbc bf-cfb bf-ecb bf-ofb
                 Blowfish Cipher

       cast cast-cbc
                 CAST Cipher

       cast5-cbc cast5-cfb cast5-ecb cast5-ofb
                 CAST5 Cipher

       des des-cbc des-cfb des-ecb des-ede des-ede-cbc des-ede-cfb des-ede-ofb des-ofb
                 DES Cipher

       des3 desx des-ede3 des-ede3-cbc des-ede3-cfb des-ede3-ofb
                 Triple-DES Cipher

       idea idea-cbc idea-cfb idea-ecb idea-ofb
                 IDEA Cipher

       rc2 rc2-cbc rc2-cfb rc2-ecb rc2-ofb
                 RC2 Cipher

       rc4       RC4 Cipher

       rc5 rc5-cbc rc5-cfb rc5-ecb rc5-ofb
                 RC5 Cipher

Next post we will discuss how to use openssl to do encryption and decryption


Source:

Wikipedia.org
Linux Man Page