Add main script + example files

Makefile

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+
+### Makefile
+
+```Makefile
+# Makefile for the Go File Encryption and Decryption project
+
+# The binary name
+BINARY_NAME = file-crypto
+
+# Build the Go binary
+build:
+	@echo "Building the Go binary..."
+	go build -o $(BINARY_NAME) main.go
+
+# Run the Go application with encryption
+encrypt:
+	@echo "Encrypting the file..."
+	./$(BINARY_NAME) encrypt example.csv encrypted.csv
+
+# Run the Go application with decryption
+decrypt:
+	@echo "Decrypting the file..."
+	./$(BINARY_NAME) decrypt encrypted.csv decrypted.csv
+
+# Clean up build files
+clean:
+	@echo "Cleaning up..."
+	rm -f $(BINARY_NAME)
+
+# Default target: build the binary
+all: build

example.csv

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+stark,lannister,tyrell,targaryen,baratheon

example.txt

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+ned stark

go.mod

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+module go-encrypt
+
+go 1.22.5

main.go

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+package main
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"fmt"
+	"io"
+	"os"
+)
+
+func main() {
+	key := []byte("example key 1234") // 16 bytes key for AES-128
+	inputFile := "example.csv"
+	encryptedFile := "encrypted.csv"
+	decryptedFile := "decrypted.csv"
+
+	// Encrypt the file
+	err := encryptFile(inputFile, encryptedFile, key)
+	if err != nil {
+		fmt.Println("Error encrypting file:", err)
+		return
+	}
+	fmt.Println("File encrypted successfully.")
+
+	// Decrypt the file
+	err = decryptFile(encryptedFile, decryptedFile, key)
+	if err != nil {
+		fmt.Println("Error decrypting file:", err)
+		return
+	}
+	fmt.Println("File decrypted successfully.")
+}
+
+// encryptFile encrypts the file at inputPath and writes the encrypted data to outputPath
+func encryptFile(inputPath, outputPath string, key []byte) error {
+	data, err := os.ReadFile(inputPath)
+	if err != nil {
+		return err
+	}
+
+	// Generate a new AES cipher using our 16, 24 or 32 bytes long key
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return err
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
+		return err
+	}
+
+	// Encrypt the data using Seal (which also appends the nonce and the encrypted data together)
+	ciphertext := gcm.Seal(nonce, nonce, data, nil)
+
+	return os.WriteFile(outputPath, ciphertext, 0644)
+}
+
+// decryptFile decrypts the file at inputPath and writes the decrypted data to outputPath
+func decryptFile(inputPath, outputPath string, key []byte) error {
+	ciphertext, err := os.ReadFile(inputPath)
+	if err != nil {
+		return err
+	}
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return err
+	}
+
+	nonceSize := gcm.NonceSize()
+	nonce, ciphertext := ciphertext[:nonceSize], ciphertext[nonceSize:]
+
+	// Decrypt the data
+	plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return err
+	}
+
+	return os.WriteFile(outputPath, plaintext, 0644)
+}