The Lightweight Encryption Algorithm is a 128-bit block cipher developed by South Korea in 2013 to provide confidentiality in high-speed environments such as big data and cloud computing, as well as lightweight environments such as IoT devices and mobile devices. LEA has three different key lengths: 128, 192, and 256 bits. LEA encrypts data about 1.5 to 2 times faster than AES, the most widely used block cipher in various software environments.
The Lightweight Encryption Algorithm (also known as LEA) is a 128-bit block cipher developed by South Korea in 2013 to provide confidentiality in high-speed environments such as big data and cloud computing, as well as lightweight environments such as IoT devices and mobile devices. LEA has three different key lengths: 128, 192, and 256 bits. LEA encrypts data about 1.5 to 2 times faster than AES, the most widely used block cipher in various software environments.
LEA is one of the cryptographic algorithms approved by the Korean Cryptographic Module Validation Program (KCMVP) and is the national standard of Republic of Korea (KS X 3246). LEA is included in the ISO/IEC 29192-2:2019 standard (Information security - Lightweight cryptography - Part 2: Block ciphers).
Contents
Specification
The block cipher LEA consisting of ARX operations (modular Addition:
⊞
{\displaystyle \boxplus }
, bitwise Rotation:
⋘
{\displaystyle \lll }
,
⋙
{\displaystyle \ggg }
, and bitwise XOR
⊕
{\displaystyle \oplus }
) for 32-bit words processes data blocks of 128 bits and has three different key lengths: 128, 192, and 256 bits.
LEA with a 128-bit key, LEA with a 192-bit key, and LEA with a 256-bit key are referred to as “LEA-128”, “LEA-192”, and “LEA-256”, respectively.
The number of rounds is 24 for LEA-128, 28 for LEA-192, and 32 for LEA-256.
Encryption
Let
P
=
P
[
0
]
‖
P
[
1
]
‖
P
[
2
]
‖
P
[
3
]
{\displaystyle P=P[0]\|P[1]\|P[2]\|P[3]}
be a 128-bit block of plaintext and
C
=
C
[
0
]
‖
C
[
1
]
‖
C
[
Decryption
The decryption operation is as follows:
X
N
r
[
0
]
‖
X
N
r
[
1
]
‖
X
N
r
[
2
]
‖
X
N
r
[
3
]
←
C
[
0
]
‖
C
[
1
]
Key schedule
The key schedule of LEA supports 128, 192, and 256-bit keys and outputs 192-bit round keys
K
i
{\displaystyle K_{i}}
(
0
≤
i
<
N
r
{\displaystyle 0\leq i<Nr}
) for the data processing part.
Let
K
=
K
[
0
]
‖
K
[
1
]
‖
K
[
2
]
‖
K
[
3
]
Security
As of 2019, no successful attack on full-round LEA is known.
As is typical for iterated block ciphers, reduced-round variants have been attacked.
The best published attacks on LEA in the standard attack model (CPA/CCA with unknown key) are boomerang attacks and differential linear attacks.
The security margin to the whole rounds ratio is greater than 37% against various existing cryptanalytic techniques for block ciphers.
Performance
LEA has very good performance in a general-purpose software environment.
In particular, it is possible to encrypt at a rate of about 1.5 to 2 times on average, compared to AES, the most widely used block cipher in various software environments.
The tables below compare the performance of LEA and AES using FELICS (Fair Evaluation of Lightweight Cryptographic Systems), a benchmarking framework for evaluation of software implementations of lightweight cryptographic primitives.
Test vectors
Test vectors for LEA for each key length are as follows.
