aes-eiffel

aes-eiffel is an Eiffel implementation of the Advanced Encryption Standard (AES) algorithm, based on the tiny-AES-c C implementation. This library provides a simple and efficient way to perform AES encryption and decryption in Eiffel applications.

Features

• Supports AES-128, AES-192 and AES-256 encryption and decryption.
• Implements three modes of operation:
  • ECB (Electronic Codebook)
  • CBC (Cipher Block Chaining)
  • CTR (Counter)
• Provides string-based operations for easy encryption and decryption of text
• Includes PKCS7 padding for block alignment
• Designed for simplicity and ease of use

Usage

The library provides three main methods for each mode of operation:

1. ECB Mode:

   • ecb_encoding_string(plaintext, key): STRING
   • ecb_decoding_string(ciphertext, key): STRING

2. CBC Mode:

   • cbc_encoding_string(plaintext, key, iv): STRING
   • cbc_decoding_string(ciphertext, key, iv): STRING

3. CTR Mode:

   • ctr_encoding_string(plaintext, key, nonce): STRING
   • ctr_decoding_string(ciphertext, key, nonce): STRING

Example usage:

    local
        aes: AES
        key, plaintext, encrypted, decrypted: STRING
    do
        create aes.make
        key := "Sixteen byte key"
        plaintext := "Hello, World!"
        encrypted := aes.ecb_encoding_string(plaintext, key)
        decrypted := aes.ecb_decoding_string(encrypted, key)
        check plaintext.is_equal(decrypted) end
    end

Security Considerations

• CTR (Counter) mode is generally considered more secure and preferable compared to ECB and CBC modes.1
• ECB mode is the least secure and should be avoided for most use cases, especially for data larger than a single block.3
• CTR mode offers advantages over CBC:
  • Better performance on multi-core systems due to easier parallelization.1
  • No risks associated with padding.4
• Key security considerations:
  • Proper key management is crucial for all modes.5
  • CTR mode requires unique nonces (IVs) for each encryption operation.6
  • For maximum security, authenticated encryption modes like GCM (which builds on CTR) are recommended.7
• While CTR is generally more secure than CBC or ECB, combining CTR with a proper authentication mechanism or using an authenticated encryption mode like GCM is the most secure approach.8
• Always use a secure method to generate keys and IVs/nonces.9