eolib.encrypt

Utilities to handle EO data encryption.

interleave(data) → None[source]

Interleaves a sequence of bytes. When encrypting EO data, bytes are “woven” into each other.

Used when encrypting packets and data files.

Example

>>> interleave([0, 1, 2, 3, 4, 5])
[0, 5, 1, 4, 2, 3]

This is an in-place operation.

Parameters:

data (bytearray) – The data to interleave.

deinterleave(data) → None[source]

Deinterleaves a sequence of bytes. This is the reverse of interleave.

Used when decrypting packets and data files.

Example

>>> deinterleave([0, 1, 2, 3, 4, 5])
[0, 2, 4, 5, 3, 1]

This is an in-place operation.

Parameters:

data (bytearray) – The data to deinterleave.

flip_msb(data) → None[source]

Flips the most significant bits of each byte in a sequence of bytes. (Values 0 and 128 are not flipped.)

Used when encrypting and decrypting packets.

Example

>>> flip_msb([0, 1, 127, 128, 129, 254, 255])
[0, 129, 255, 128, 1, 126, 127]

This is an in-place operation.

Parameters:

data (bytearray) – The data to flip most significant bits on.

swap_multiples(data, multiple) → None[source]

Swaps the order of contiguous bytes in a sequence of bytes that are divisible by a given multiple value.

Used when encrypting and decrypting packets and data files.

Example

>>> swap_multiples([10, 21, 27], 3)
[10, 27, 21]

This is an in-place operation.

Parameters:

  • data (bytearray) – The data to swap bytes in.

  • multiple (int) – The multiple value.

Raises:

ValueError – If multiple is less than 1.

server_verification_hash(challenge) → int[source]

This hash function is used by the game client to verify communication with a genuine server during connection initialization.

Parameters:

challenge (int) – The challenge value sent by the client. Should be no larger than 11,092,110.

Returns:

The hashed challenge value.

Remarks

  • The client sends an integer value to the server in the INIT_INIT client packet, where it is referred to as the challenge.

  • The server hashes the value and sends the hash back in the INIT_INIT server packet.

  • The client hashes the value and compares it to the hash sent by the server.

  • If the hashes do not match, the client drops the connection.

Warning

Oversized challenges may result in negative hash values, which cannot be represented properly in the EO protocol.

See also