# TgCrypto

<img src="https://i.imgur.com/JyxrStE.png" width="160" align="right">

> Fast Telegram Crypto Library for Python

**TgCrypto** is a high-performance, easy-to-install Telegram Crypto Library written in C as a Python extension.
TgCrypto is intended for [Pyrogram](//github.com/pyrogram/pyrogram) and implements the crypto algorithms Telegram
requires, namely **AES-IGE 256 bit** (used in MTProto v2.0) and **AES-CTR 256 bit** (used for CDN encrypted files).

## Installation

``` bash
$ pip3 install --upgrade tgcrypto
```

More info: https://docs.pyrogram.org/topics/tgcrypto

## API

TgCrypto API consists of these four methods:

```python
def ige256_encrypt(data: bytes, key: bytes, iv: bytes) -> bytes:

def ige256_decrypt(data: bytes, key: bytes, iv: bytes) -> bytes:

def ctr256_encrypt(data: bytes, key: bytes, iv: bytes, state: bytes) -> bytes:

def ctr256_decrypt(data: bytes, key: bytes, iv: bytes, state: bytes) -> bytes:
```

## Usage

### IGE Mode

**Note**: Data must be padded to match a multiple of the block size (16 bytes).

``` python
import os
import tgcrypto

data = os.urandom(10 * 1024 * 1024 + 7)  # 10 MB of random data + 7 bytes to show padding
key = os.urandom(32)  # Random Key
iv = os.urandom(32)  # Random IV

# Pad with zeroes: -7 % 16 = 9
data += bytes(-len(data) % 16)

ige_encrypted = tgcrypto.ige256_encrypt(data, key, iv)
ige_decrypted = tgcrypto.ige256_decrypt(ige_encrypted, key, iv)

print(data == ige_decrypted)  # True
```
    
### CTR Mode (single chunk)

``` python
import os
import tgcrypto

data = os.urandom(10 * 1024 * 1024)  # 10 MB of random data

key = os.urandom(32)  # Random Key

enc_iv = bytearray(os.urandom(16))  # Random IV
dec_iv = enc_iv.copy()  # Keep a copy for decryption

ctr_encrypted = tgcrypto.ctr256_encrypt(data, key, enc_iv, bytes(1))
ctr_decrypted = tgcrypto.ctr256_decrypt(ctr_encrypted, key, dec_iv, bytes(1))

print(data == ctr_decrypted)  # True
```

### CTR Mode (stream)

``` python
import os
import tgcrypto
from io import BytesIO

data = BytesIO(os.urandom(10 * 1024 * 1024))  # 10 MB of random data

key = os.urandom(32)  # Random Key

enc_iv = bytearray(os.urandom(16))  # Random IV
dec_iv = enc_iv.copy()  # Keep a copy for decryption

enc_state = bytes(1)  # Encryption state, starts from 0
dec_state = bytes(1)  # Decryption state, starts from 0

encrypted_data = BytesIO()  # Encrypted data buffer
decrypted_data = BytesIO()  # Decrypted data buffer

while True:
    chunk = data.read(1024)

    if not chunk:
        break

    # Write 1K encrypted bytes into the encrypted data buffer
    encrypted_data.write(tgcrypto.ctr256_encrypt(chunk, key, enc_iv, enc_state))

# Reset position. We need to read it now
encrypted_data.seek(0)

while True:
    chunk = encrypted_data.read(1024)

    if not chunk:
        break

    # Write 1K decrypted bytes into the decrypted data buffer
    decrypted_data.write(tgcrypto.ctr256_decrypt(chunk, key, dec_iv, dec_state))

print(data.getvalue() == decrypted_data.getvalue())  # True
```

## License

[LGPLv3+](COPYING.lesser) © 2017-2019 [Dan](https://github.com/delivrance)