What is Crypt::ECB

A quick introduction is provided for the Crypt::ECB Perl module, which can be used to perform encryption and decryption in the ECB (Electronic CodeBook) operation mode with a given block cipher for any number of blocks.

What Is Crypt::ECB? Crypt::ECB is a Perl module providing ECB (Electronic CodeBook) block cipher operation mode functionality. Crypt::ECB was developed by Christoph Appel.

Here is the description of Crypt::ECB on the cpan.org Web site: "This module is a Perl-only implementation of the ECB mode. In combination with a block cipher such as DES, IDEA or Blowfish, you can encrypt and decrypt messages of arbitrarily long length. Though for security reasons other modes than ECB such as ECB should be preferred. See textbooks on cryptography if you want to know why."

In case you forgot how ECB (Electronic CodeBook) works, here a shortest version of the ECB algorithm:

```
Input:
P: The plaintext in multiple blocks
K: The secret key
E(K,B): The block encryption function

Output:
C: The ciphertext in multiple blocks

Algorithm - ECB (Electronic CodeBook) Operation Mode:
(P[1], P[2], P[3},...) = P    : Split plaintext into blocks

Loop i over 1,2,3,...
C[i] = E(K, P[i])
End Loop

C = (C[1], C[2], C[3},...)    : Concatenate ciphertext blocks
```

The ECB algorithm can also be illustrated by this simple diagram:

```Algorithm - ECB (Electronic CodeBook) Operation Mode:

P[1]   P[2]   P[3] ...
|      |      |
E(K)   E(K)   E(K)
|      |      |
C[1]   C[2]   C[3]
```

Crypt::ECB module offers the following major methods to perform the ECB operation algorithm described above. Other methods will be discussed later as needed.

\$c = Crypt::ECB->new(\$key, \$algorithm) - Returns a new Crypt::ECB cipher operation object with a given secret key and given cipher algorithm. To use Crypt::ECB with Crypt::Blowfish, you need to specify \$algorithm = 'Blowfish'. The secret key must be between 8 bytes and 56 bytes long, when Crypt::Blowfish is used.

\$c->start('encrypting|decrypting') - Initialize the cipher operation object \$c to start a new encryption or decryption operation.

\$c->crypt(\$text) - Returns the next output block from the current encryption or decryption operation with the given extra input. This method is designed to be used in a loop to encrypt or decrypt large input in chunks.

\$c->finish() - Returns the last output block from the current encryption or decryption operation.

\$c->encrypt(\$plaintext) - Returns the ciphertext as the encryption output from the specified plaintext.

\$c->decrypt(\$ciphertext) - Returns the plaintext as the decryption output from the specified ciphertext.