"bf-ofb" Cipher with Salted Key

A tutorial example is provided to show you how to use the 'bf-ofb' cipher with Salted Key to encrypt and decrypt binary data files. The Secret Key and the IV will be derived from the given passphrase and the given salt.

Similar to the OpenSSL "enc -bf-ecb" command, we can also run the "enc -bf-ofb" command in the "Salted Key" way by using "-pass" and "-S" options:

Here is my first test using OpenSSL "enc -bf-ofb" command in the "Salted Key" way with "-pass pass:" and "-S" options.

   perl -e "binmode(STDOUT); print pack('H*', '0000000000000000')" 
   > 2-block.txt

   perl -e "binmode(STDOUT); print pack('H*', '0000000000000000')" 
   >> 2-block.txt

C:\herong>\local\gnuwin32\bin\openssl enc -bf-ofb -e 
   -pass pass:MySecret -S 0000000000000000 
   -in 2-block.txt -out cipher.txt -nopad -p
iv =6FF60FCD91D7F34E

C:\herong>perl -e "print unpack('H*',v>)" < cipher.txt
53616c7465645f5f 0000000000000000 606a204b0f2aab9c7762557547f3ea05
---------------- ---------------- --------------------------------
   "Salted__"          Salt           Cipher blocks

C:\herong>\local\gnuwin32\bin\openssl enc -bf-ofb -d 
   -pass pass:MySecret -in cipher.txt -out decrypted.txt -nopad -p
iv =6FF60FCD91D7F34E

C:\herong>perl -e "while (read(STDIN,$_,1)){print unpack('H*',$_);}" 
   < decrypted.txt

The output confirms that:

Another interesting note is that when plaintext is a stream of 0x00, both CBC and OFB operation modes generate the same ciphertext.

Last update: 2015.

Table of Contents

 About This Book

 Blowfish Cipher Algorithm

 Perl Crypt::Blowfish Module

 Perl Crypt::ECB Perl Module

 Perl Crypt::CBC Module

 Perl Crypt::CFB Perl Module

 OpenSSL "enc -bf-ecb" for Blowfish/ECB Encryption

 OpenSSL "enc -bf-cbc" for Blowfish/CBC Encryption

 OpenSSL "enc -bf-cfb" for Blowfish/CFB Encryption

OpenSSL "enc -bf-ofb" for Blowfish/OFB Encryption

 "bf-ofb" Cipher with Literal Key

 "bf-ofb" Cipher on Multiple Blocks

 "bf-ofb" Encryption Verification

 "bf-ofb" 2-Block Test Vectors

"bf-ofb" Cipher with Salted Key

 "bf-ofb" Cipher with Random Salt

 "enc -bf-ofb" Command Summary


 PDF Printing Version