AES ECB Encryption in Go: Troubleshooting and Implementation

Your initial attempt to implement AES ECB encryption in Go encountered some roadblocks. Here's a comprehensive explanation and a revised code solution:

PKCS5 Padding

PKCS5 padding is crucial for AES encryption in ECB mode. It ensures that the plaintext has a length that's a multiple of the block size. Your existing PKCS5Pad algorithm seems to be functioning correctly.

Encryption Mode

The Go AES package doesn't explicitly provide an "ECB" mode setting. However, you can emulate it by decrypting the data in fixed-size blocks:

Revised Encrypted Function

func AESECB(ciphertext []byte) []byte {
    cipher, _ := aes.NewCipher([]byte(KEY))
    bs := aes.BlockSize
    if len(ciphertext)%bs != 0 {
        panic("Need a multiple of the block size")
    }
    plaintext := make([]byte, len(ciphertext))
    for len(plaintext) > 0 {
        cipher.Decrypt(plaintext, ciphertext)
        plaintext = plaintext[bs:]
        ciphertext = ciphertext[bs:]
    }
    return plaintext
}

This code splits the ciphertext into blocks, decrypts each block, and appends the decrypted blocks to the plaintext buffer.

Implementation Issue

The revised AESECB function doesn't seem to be returning any data. Ensure that you're calling it correctly and passing in the encrypted ciphertext as an argument.

Important Security Note

It's noteworthy that ECB mode is not cryptographically secure. Repeated plaintext blocks always produce identical encrypted blocks, making it vulnerable to certain attacks. It's highly recommended to use more secure modes of operation, such as CBC, CTR, or GCM, for robust encryption.