aes_encryption.sh

#!/bin/bash

# Function to list all files except .txt files and allow user selection by number
select_file() {
    echo "Available files:"
    local i=1
    for file in *; do
        if [[ $file != *.txt ]]; then
            echo "$i) $file"
            files[i++]="$file"
        fi
    done

    read -p "Select a file by number: " file_number
    filename="${files[file_number]}"

    if [ -z "$filename" ] || [ ! -f "$filename" ]; then
        echo "Invalid selection or file does not exist."
        exit 1
    fi
}

# Function to format the output filename
format_output_filename() {
    local base_name="${1%.*}"
    local extension="${1##*.}"
    base_name=$(echo "$base_name" | sed -e 's/_encrypted$//' -e 's/_decrypted$//')
    echo "${base_name}_${2}.${extension}"
}

# Function to ask for encryption/decryption
select_operation() {
    echo "Select operation:"
    echo "1) Encrypt"
    echo "2) Decrypt"

    read -p "Enter your choice (1 or 2): " operation_choice

    case $operation_choice in
        1) operation="encrypt" ;;
        2) operation="decrypt" ;;
        *) echo "Invalid operation."
           exit 1 ;;
    esac
}

# Function to get passphrase from user
get_user_input() {
    read -p "Enter passphrase: " passphrase
}

# Function to perform the encryption or decryption
perform_operation() {
    local iter=10000
    local output_filename

    if [ "$operation" == "encrypt" ]; then
        local iv=$(openssl rand -hex 16)
        output_filename=$(format_output_filename "$filename" "encrypted")
        openssl enc -aes-256-cbc -e -in "$filename" -pass "pass:$passphrase" -pbkdf2 -iter $iter -iv "$iv" | xxd -p -c 256 | cat <(echo -n "$iv") - > "$output_filename"
        echo "Encryption complete. Output: $output_filename"
    elif [ "$operation" == "decrypt" ]; then
        local iv=$(head -c 32 "$filename")
        output_filename=$(format_output_filename "$filename" "decrypted")
        xxd -r -p <(tail -c +33 "$filename") > temp_decrypted
        openssl enc -aes-256-cbc -d -in temp_decrypted -out "$output_filename" -pass "pass:$passphrase" -pbkdf2 -iter $iter -iv "$iv"
        rm temp_decrypted
        echo "Decryption complete. Output: $output_filename"
    fi
}

# Main script logic
select_file
select_operation
get_user_input
perform_operation