Blowfish Cipher Tutorials - Herong's Tutorial Examples - v2.03, by Herong Yang
Crypt::CBC Operation Simulation
A tutorial Perl example is provided to show how to use Crypt::Blowfish module to simulate the CBC operation mode. The simulation result matches the result from the Crypt::CBC module.
So far, we have learned how to use Crypt::Blowfish to encrypt a single block of plaintext. We have also learned how to use Crypt::CBC to encrypt blocks of plaintext with direct control of secret key and IV. We should be able to verify Crypt::CBC encryption results by simulating the CBC algorithm with Crypt::CBC module.
Here is my example Perl script, Crypt-CBC-Blowfish-Simulation.pl, that simulates the CBC operation by calling Crypt::Blowfish one block at time. It also verifies the ciphertext by calling the Crypt::CBC module directly.
#- Crypt-CBC-Blowfish-Simulation.pl #- Copyright (c) 2015 HerongYang.com, All Rights Reserved. #- use Crypt::CBC; use Crypt::Blowfish; my ($keyHex, $ivHex, $plainHex) = @ARGV; print("Crypt::CBC Blowfish Simulation - output in Hex:\n"); $keyHex = "1122334455667788" unless $keyHex; $ivHex = "0000000000000000" unless $ivHex; $plainHex = "0123456789abcdef" unless $plainHex; $keyStr = pack("H*", $keyHex); $ivStr = pack("H*", $ivHex); $plainStr = pack("H*", $plainHex); print(" Secret Key ($keyHex)\n"); print(" IV ($ivHex)\n"); print(" Plaintext ($plainHex)\n"); print("Creating Crypt::Blowfish Object ...\n"); $blowfish = new Crypt::Blowfish($keyStr); $count = 0; $cipherHexPrev = $ivHex; while ($plainHex) { $count++; $plainHexBlock = substr($plainHex,0,16); $plainHex = substr($plainHex,16); print("Simulating CBC on block $count...\n"); print(" Prev ciphertext ($cipherHexPrev)\n"); print(" Plaintext ($plainHexBlock)\n"); $cipherStrPrev = pack("H*", $cipherHexPrev); $plainStrBlock = pack("H*", $plainHexBlock); $xorStrBlock = $cipherStrPrev ^ $plainStrBlock; $xorHexBlock = unpack("H*", $xorStrBlock); print(" Plaintext XORed ($xorHexBlock)\n"); $cipherStrBlock = $blowfish->encrypt($xorStrBlock); $cipherHexBlock = unpack("H*", $cipherStrBlock); print(" Ciphertext ($cipherHexBlock)\n"); $cipherHexPrev = $cipherHexBlock; } print("Creating Crypt::CBC Object ...\n"); $blowfish = new Crypt::Blowfish($keyStr); $cipher = Crypt::CBC->new( -cipher => $blowfish, -iv => $ivStr, -header => 'none', -padding => 'none' ); print("Encrypting entire plaintext with Crypt::CBC...\n"); $cipherStr = $cipher->encrypt($plainStr); $cipherHex = unpack("H*", $cipherStr); print(" Ciphertext ($cipherHex)\n");
The key part of the CBC mode simulation is the following logics used in CBC mode:
Now try this example script with different size plaintext:
C:\Herong>perl Crypt-CBC-Blowfish-Simulation.pl \ 1122334455667788 0000000000000000 0123456789abcdef Crypt::CBC Blowfish Simulation - output in Hex: Secret Key (1122334455667788) IV (0000000000000000) Plaintext (0123456789abcdef) Creating Crypt::Blowfish Object ... Simulating CBC on block 1... Prev ciphertext (0000000000000000) Plaintext (0123456789abcdef) Plaintext XORed (0123456789abcdef) Ciphertext (103248f0eea98e89) Creating Crypt::CBC Object ... Encrypting entire plaintext with Crypt::CBC... Ciphertext (103248f0eea98e89) C:\Herong>perl Crypt-CBC-Blowfish-Simulation.pl 1122334455667788 \ 0000000000000000 0123456789abcdef0123456789abcdef Crypt::CBC Blowfish Simulation - output in Hex: Secret Key (1122334455667788) IV (0000000000000000) Plaintext (0123456789abcdef0123456789abcdef) Creating Crypt::Blowfish Object ... Simulating CBC on block 1... Prev ciphertext (0000000000000000) Plaintext (0123456789abcdef) Plaintext XORed (0123456789abcdef) Ciphertext (103248f0eea98e89) Simulating CBC on block 2... Prev ciphertext (103248f0eea98e89) Plaintext (0123456789abcdef) Plaintext XORed (11110d9767024366) Ciphertext (8f5e452a60506163) Creating Crypt::CBC Object ... Encrypting entire plaintext with Crypt::CBC... Ciphertext (103248f0eea98e898f5e452a60506163) C:\Herong>perl Crypt-CBC-Blowfish-Simulation.pl \ 1122334455667788 1111111111111111 0123456789abcdef0123456789abcdef0123456789abcdef Crypt::CBC Blowfish Simulation - output in Hex: Secret Key (1122334455667788) IV (1111111111111111) Plaintext (0123456789abcdef0123456789abcdef0123456789abcdef) Creating Crypt::Blowfish Object ... Simulating CBC on block 1... Prev ciphertext (1111111111111111) Plaintext (0123456789abcdef) Plaintext XORed (1032547698badcfe) Ciphertext (c3a27e1f67d146f0) Simulating CBC on block 2... Prev ciphertext (c3a27e1f67d146f0) Plaintext (0123456789abcdef) Plaintext XORed (c2813b78ee7a8b1f) Ciphertext (dd89a07b06cad2aa) Simulating CBC on block 3... Prev ciphertext (dd89a07b06cad2aa) Plaintext (0123456789abcdef) Plaintext XORed (dcaae51c8f611f45) Ciphertext (2cd3a609b55defca) Creating Crypt::CBC Object ... Encrypting entire plaintext with Crypt::CBC... Ciphertext (c3a27e1f67d146f0dd89a07b06cad2aa2cd3a609b55defca) C:\Herong>perl Crypt-CBC-Blowfish-Simulation.pl \ 1122334455667788 ffffffffffffffff \ 0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef Crypt::CBC Blowfish Simulation - output in Hex: Secret Key (1122334455667788) IV (ffffffffffffffff) Plaintext (0123456789abcdef0123456789abcdef 0123456789abcdef0123456789abcdef) Creating Crypt::Blowfish Object ... Simulating CBC on block 1... Prev ciphertext (ffffffffffffffff) Plaintext (0123456789abcdef) Plaintext XORed (fedcba9876543210) Ciphertext (2b41e1b29adaa3ab) Simulating CBC on block 2... Prev ciphertext (2b41e1b29adaa3ab) Plaintext (0123456789abcdef) Plaintext XORed (2a62a4d513716e44) Ciphertext (2149531ce57439d0) Simulating CBC on block 3... Prev ciphertext (2149531ce57439d0) Plaintext (0123456789abcdef) Plaintext XORed (206a167b6cdff43f) Ciphertext (54061f6cddc380e2) Simulating CBC on block 4... Prev ciphertext (54061f6cddc380e2) Plaintext (0123456789abcdef) Plaintext XORed (55255a0b54684d0d) Ciphertext (713fa4974566fdfd) Creating Crypt::CBC Object ... Encrypting entire plaintext with Crypt::CBC... Ciphertext (2b41e1b29adaa3ab2149531ce57439d0 54061f6cddc380e2713fa4974566fdfd)
The output looks good. The ciphertext blocks produced from the simulation logic match well with the Crypt::CBC module in all 4 tests.
Table of Contents
Installing Crypt::CBC 2.33 with ActivePerl
Crypt::CBC Encryption with Literal Keys
Crypt::CBC Literal Key Error Cases
Crypt::CBC Encryption with Crypt::Blowfish Objects
►Crypt::CBC Operation Simulation
Crypt::CBC Encryption Verification
Blowfish CBC 2-Block Test Vectors
Crypt::CBC Prepending IV to Ciphertext
Crypt::CBC Encryption with Salted Keys
Crypt::CBC Salted Key Test Cases
Crypt::CBC Secret Key and IV Algorithm
Crypt::CBC Encryption with Random Salt
Crypt::CBC Padding Option Tests
Crypt::CBC Blowfish Encryption Summary
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