AES Encryption in Kotlin

Enjoy secure encryption with AES in Kotlin! 🚀

This repository provides a Kotlin implementation of the Advanced Encryption Standard (AES), ported from the original aes-js library. It supports AES encryption and decryption with various modes of operation, including ECB, CBC, CFB, OFB, and CTR.

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Features

• AES Encryption and Decryption: Supports 128-bit, 192-bit, and 256-bit keys.
• Modes of Operation:
  • ECB (Electronic Codebook)
  • CBC (Cipher Block Chaining)
  • CFB (Cipher Feedback)
  • OFB (Output Feedback)
  • CTR (Counter)
• PKCS#7 Padding: Automatically pads and strips data for block alignment.
• Easy-to-Use API: Simple and intuitive methods for encryption and decryption.

Installation

Add the following dependency to your build.gradle.kts file:

implementation("io.github.niyajali:aes-kotlin:1.0.1")

Usage

1. AES Encryption Basics

Initialize AES with a Key

val key = "2b7e151628aed2a6abf7158809cf4f3c".hexToBytes() // 128-bit key
val aes = AESEncryption(key)

Encrypt and Decrypt Data

val plaintext = "Hello, AES!".toByteArray()
val ciphertext = aes.encrypt(plaintext)
val decryptedText = aes.decrypt(ciphertext)

println("Ciphertext: ${ciphertext.toHexString()}")
println("Decrypted Text: ${String(decryptedText)}")

2. Modes of Operation

ECB (Electronic Codebook)

val ecb = ModeOfOperationECB(key)
val encrypted = ecb.encrypt(plaintext)
val decrypted = ecb.decrypt(encrypted)

CBC (Cipher Block Chaining)

val iv = "000102030405060708090a0b0c0d0e0f".hexToBytes() // Initialization Vector
val cbc = ModeOfOperationCBC(key, iv)
val encrypted = cbc.encrypt(plaintext)
val decrypted = cbc.decrypt(encrypted)

CFB (Cipher Feedback)

val cfb = ModeOfOperationCFB(key, iv, segmentSize = 8) // 8-bit segment size
val encrypted = cfb.encrypt(plaintext)
val decrypted = cfb.decrypt(encrypted)

OFB (Output Feedback)

val ofb = ModeOfOperationOFB(key, iv)
val encrypted = ofb.encrypt(plaintext)
val decrypted = ofb.decrypt(encrypted)

CTR (Counter)

val counter = Counter("f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff".hexToBytes())
val ctr = ModeOfOperationCTR(key, counter)
val encrypted = ctr.encrypt(plaintext)
val decrypted = ctr.decrypt(encrypted)

3. PKCS#7 Padding

Pad Data

val paddedData = pkcs7Pad(plaintext, 16) // Pad to 16-byte blocks

Strip Padding

val strippedData = pkcs7Strip(paddedData)

4. Utility Functions

Convert Bytes to Hex String

val hexString = bytesToHex(ciphertext)
println("Hex: $hexString")

Convert Hex String to Bytes

val bytes = "2b7e151628aed2a6abf7158809cf4f3c".hexToBytes()

Example

Here’s a complete example of encrypting and decrypting data using AES in CBC mode:

fun main() {
    val key = "2b7e151628aed2a6abf7158809cf4f3c".hexToBytes()
    val iv = "000102030405060708090a0b0c0d0e0f".hexToBytes()
    val plaintext = "Hello, AES!".toByteArray()

    // Encrypt
    val cbc = ModeOfOperationCBC(key, iv)
    val ciphertext = cbc.encrypt(plaintext)
    println("Encrypted: ${bytesToHex(ciphertext)}")

    // Decrypt
    val decrypted = cbc.decrypt(ciphertext)
    println("Decrypted: ${String(decrypted)}")
}

Contributing

Contributions are welcome! If you find any issues or have suggestions for improvements, please open an issue or submit a pull request.

License

This project is licensed under the MIT License. See the LICENSE file for details.

Acknowledgments

• This library is a Kotlin port of the original aes-js library by ricmoo.
• Special thanks to the contributors and maintainers of the original library.