Electronic Code Book (ECB) in Cryptography

Electronic Code Book (ECB) is the simplest AES block cipher mode. A block cipher takes a fixed-size block of text (b bits) and a key and outputs a block of b-bit encrypted text. If the number of plaintexts to be encrypted is greater than b bits, then the block cipher can still be used by breaking the plaintext into b-bit blocks. As multiple blocks of plaintexts are encrypted using the same key, there come several security problems. A mode of operation (or mode of operation) is a way to make a cryptographic algorithm stronger or to change the algorithm for a particular application, such as a block cipher applied to a set of blocks or a stream of data. for high-speed requirements

Electronic Code Book (ECB) in cryptography

The most basic mode is electronic codebook mode, where the plain text is processed block by block and each block is encrypted using a single key. The term codebook is in itself self-explaining. If we are given a particular key, then we have a unique ciphertext for every b-bit block of plaintext. Thus, one can visualize a large codebook with entries for all conceivable b-bit plaintext patterns showing its corresponding ciphertext. This is because it is important to understand how the ECB Mode works and in what context this method is better than the others.

NIST Five Modes of Operation to Apply a Block Cipher

These modes are designed to be used for any symmetric block cipher, including triple DES and AES. The five modes are designed to cover a wide variety of applications of encryption for which a block cipher could be used.

Working of Electronic Code Book

In ECB encryption, plaintext is divided into fixed size blocks, usually b bits a piece, and then encrypted block by block, all using the same key. If the message is longer than the block size, padding is applied to the last block as necessary.

In a schematic representation (as seen in above and below figures), the plaintext, padded if needed, is segmented into b-bit blocks labeled P1, P2, ..., PN. Each block undergoes encryption to produce the corresponding ciphertext blocks labeled C1, C2, ..., CN. The encryption and decryption operations are straightforward:

Encryption:

?_?=?(?,?_?), ?=1,2,...,?

Decryption:

?_?=?(?,?_?), ?=1,2,...,?

Electronic Code Book (ECB) Security Challenges

ECB was initially designed to protect messages that never exceed a single block. For example, it was used to encrypt keys for other purposes. However, if you use it to encrypt a message that’s longer than one block, you’ll lose a bit of data per block. That’s because it allows malicious actors to mask when two plain text blocks are identical or different.

For example, consider photograph encryption. Even though it’s encrypted, the nature of the encryption allows the outline of the photograph to be clearly visible. It’s not that the encryption has failed, it’s that it’s being used in an operation that wasn’t designed to encrypt more than one block. Internet protocols use an operation that isn’t designed for encrypting more than one block, which introduces security risks.

Electronic Code Book (ECB) Example

Consider the following example:

• Plaintext:

Binary: 10100010001110101001 Divided into blocks of 4 bits:

• Key (K):

Length: 4 bits Example key: 1011 (in hexadecimal: B)

• Encryption Process (using XOR): Encrypt each block of plaintext (Pi) with the key (K).

• Plaintext block: 1010 0010 0011 1010 1001
• Key (k): 1011
• Result XOR:

1010 ⊕ 1011 = 0001

0010 ⊕ 1011 = 1001

0011 ⊕ 1011 = 1000

1010 ⊕ 1011 = 0001

1001 ⊕ 1011 = 0010

• The final encrypted result is:

0001 1001 1000 0001 0010 (in binary)

19812 (in hexadecimal)

Advantages of Electronic Code Book

• ECB encryption is remarkably easy to implement and conceptualize. Each block of plaintext is independently encrypted with the same key. The simplicity of ECB mode makes it attractive where ease of implementation and efficiency are desirable. Designers can easily insert ECB encryption into a system without having to deal with the complexities of interleaving or feedback.

• Another important attribute of ECB mode is its resilience to the loss or corruption of individual blocks during transmission. Each ciphertext block Ci is generated independently of other blocks, which means that loss or corruption of one block does not leak into the neighboring blocks. This is especially important in systems where data is transmitted over networks where individual blocks may be treated as independent packets. Even if some blocks are lost or corrupted while in transit, the remaining blocks can be decrypted successfully, ensuring the message's integrity.

Drawbacks of Electronic Code Book

There are some drawbacks when using ECB:

• ECB relies on simple substitution instead of an initialization vector and chaining. These features make ECB easy to implement. But this is also its greatest disadvantage. When two blocks of plaintext are identical, they result in two corresponding blocks of ciphertext.

• ECB cannot be used with low block sizes (i.e., less than 40 bits) and the same encryption modes. With low block sizes, certain words and sentences in plain text may be frequently repeated in encrypted text. This means that encrypted text can contain (and expose) patterns that are derived from the same plain text. It also means that the same recurring part-blocks in plain text can appear in encrypted text. The presence of clear plain text patterns creates an opportunity for attackers to infer these patterns and execute codebook attacks.

• The Encryption Layer is weak, but can be improved by adding random pad bits to each block. The block size (64-bit or greater) is likely to have enough unique parameters, (entropy), to prevent a codebook compromise.

Conclusion

The simplest of all AES block ciphers is Electronic Code Book mode. It individually encodes each plaintext block with the same key. Its simplicity comes at its cost. Replicating the same plaintext block results in identical ciphertext blocks. That exposes a pattern in the encrypted data; hence, the application of ECB mode is only suitable when dealing with single-value encryption, for example, the transmission of a key.

There is a need to understand how to operate ECB, its terms such as keys, plaintext, and ciphertext. ECB is very easy to implement and resilient against block loss, but it is vulnerable against codebook attacks. It is not suitable for long messages. Other modes such as CBC, CFB, OFB, and CTR provide more secure alternatives in different applications.