MechMK1 · April 1, 2023 01:53
diff --git a/decrypt.js b/decrypt.js
 // This function "converts" a Uint8Array to a CryptoKey object
 // Consider this "Boilerplate" code, that doesn't do anything useful.
 function importKey(rawKey) {
    return window.crypto.subtle.importKey("raw", rawKey, "AES-GCM", true, ["encrypt", "decrypt"]);
 }

 // This function takes raw bytes and decodes them to utf-8
 function decode(bytes) {
    // Even though utf-8 is the default, it's always good to be explicit
    return new TextDecoder("utf-8").decode(bytes);
 }

 // This function takes a ciphertext, IV and key and returns the raw decrypted bytes
 async function decrypt(ciphertext, iv, key) {
    let plaintext = await crypto.subtle.decrypt({"name":"AES-GCM","iv":iv}, key, ciphertext);
    return plaintext;
 }

 // This is the "raw" key as byte array. You need to call importKey() to convert it to a CryptoKey object
 const rawKey = new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8])
 const key = await importKey(rawKey);

 // This converts the IV from Base64 to a Uint8Array aka byte array
 const iv = Uint8Array.from(atob('BtVccNu+6J1zIFjCZ6GY3w=='), c => c.charCodeAt(0))
 // Same for the ciphertext
 const ciphertext = Uint8Array.from(atob('hZFOn9mywZCC/HNaqctHtLxX/6RFuvVY7NId3LE='), c => c.charCodeAt(0))

 // This decrypts the plain bytes, then writes the decoded text to the console
 let plainBytes = await decrypt(ciphertext, iv, key)
 console.log(decode(plainBytes))
diff --git a/encryption.py b/encryption.py
 # base64 is not strictly necessary. It's just to transfer raw bytes from Python to JavaScript
 import base64

 # PyCryptodrome is used to handle all the encryption and decryption. It is necessary
 try:
    from Crypto.Cipher import AES
 except ImportError:
    print("You need to install PyCryprodome")
    print("$ pip install pycryptodome")
    exit()

 def main():
    # This represents the key [1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8]
    # A valid AES key needs to be exactly 16, 24 or 32 bytes long
    key = b'\x01\x02\x03\x04\x05\x06\x07\x08\x01\x02\x03\x04\x05\x06\x07\x08'

    # This is the data to be encrypted. It needs to be in "raw byte" form. In Python, this is the "bytes" datatype.
    # the .encode() function is used to convert a string to a byte array
    # The "utf-8" parameter just explicitly states that this string was utf-8
    data = "Hello, World!".encode("utf-8")

    # This initializes a new STATEFUL object, with the given AES key and GCM as mode.
    cipher = AES.new(key, AES.MODE_GCM)

    # This reads out the nonce / IV.
    # Quick side note: SubtleCrypto uses the name IV, while Pycryptodrome uses nonce
    # According to crypto.SE, these two are interchangable terms for GCM although nonce is "more correct".
    # I will still call it IV, since this is what JS calls it.
    iv = cipher.nonce

    # Since AES-GCM is authenticated encryption, you need both the ciphertext and the tag.
    # Pycryptodrome returns these two as separate values, but they actually belong together.
    # Specifically, the tag needs to be appended to the ciphertext!
    ciphertext, tag = cipher.encrypt_and_digest(data)
    
    # Finally, print out the IV, as well as Cipher (plus tag)
    cipherAndTag = ciphertext+tag
    print(f"IV    : {base64.b64encode(iv)}")
    print(f"Cipher: {base64.b64encode(cipherAndTag)}, {len(cipherAndTag)}")

 if __name__ == '__main__':
    main()
	// This function "converts" a Uint8Array to a CryptoKey object
	// Consider this "Boilerplate" code, that doesn't do anything useful.
	function importKey(rawKey) {
	return window.crypto.subtle.importKey("raw", rawKey, "AES-GCM", true, ["encrypt", "decrypt"]);
	}

	// This function takes raw bytes and decodes them to utf-8
	function decode(bytes) {
	// Even though utf-8 is the default, it's always good to be explicit
	return new TextDecoder("utf-8").decode(bytes);
	}

	// This function takes a ciphertext, IV and key and returns the raw decrypted bytes
	async function decrypt(ciphertext, iv, key) {
	let plaintext = await crypto.subtle.decrypt({"name":"AES-GCM","iv":iv}, key, ciphertext);
	return plaintext;
	}

	// This is the "raw" key as byte array. You need to call importKey() to convert it to a CryptoKey object
	const rawKey = new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8])
	const key = await importKey(rawKey);

	// This converts the IV from Base64 to a Uint8Array aka byte array
	const iv = Uint8Array.from(atob('BtVccNu+6J1zIFjCZ6GY3w=='), c => c.charCodeAt(0))
	// Same for the ciphertext
	const ciphertext = Uint8Array.from(atob('hZFOn9mywZCC/HNaqctHtLxX/6RFuvVY7NId3LE='), c => c.charCodeAt(0))

	// This decrypts the plain bytes, then writes the decoded text to the console
	let plainBytes = await decrypt(ciphertext, iv, key)
	console.log(decode(plainBytes))
	# base64 is not strictly necessary. It's just to transfer raw bytes from Python to JavaScript
	import base64

	# PyCryptodrome is used to handle all the encryption and decryption. It is necessary
	try:
	from Crypto.Cipher import AES
	except ImportError:
	print("You need to install PyCryprodome")
	print("$ pip install pycryptodome")
	exit()

	def main():
	# This represents the key [1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8]
	# A valid AES key needs to be exactly 16, 24 or 32 bytes long
	key = b'\x01\x02\x03\x04\x05\x06\x07\x08\x01\x02\x03\x04\x05\x06\x07\x08'

	# This is the data to be encrypted. It needs to be in "raw byte" form. In Python, this is the "bytes" datatype.
	# the .encode() function is used to convert a string to a byte array
	# The "utf-8" parameter just explicitly states that this string was utf-8
	data = "Hello, World!".encode("utf-8")

	# This initializes a new STATEFUL object, with the given AES key and GCM as mode.
	cipher = AES.new(key, AES.MODE_GCM)

	# This reads out the nonce / IV.
	# Quick side note: SubtleCrypto uses the name IV, while Pycryptodrome uses nonce
	# According to crypto.SE, these two are interchangable terms for GCM although nonce is "more correct".
	# I will still call it IV, since this is what JS calls it.
	iv = cipher.nonce

	# Since AES-GCM is authenticated encryption, you need both the ciphertext and the tag.
	# Pycryptodrome returns these two as separate values, but they actually belong together.
	# Specifically, the tag needs to be appended to the ciphertext!
	ciphertext, tag = cipher.encrypt_and_digest(data)

	# Finally, print out the IV, as well as Cipher (plus tag)
	cipherAndTag = ciphertext+tag
	print(f"IV : {base64.b64encode(iv)}")
	print(f"Cipher: {base64.b64encode(cipherAndTag)}, {len(cipherAndTag)}")

	if __name__ == '__main__':
	main()