Abstract:
In this work, we present the rst side channel collision based key recovery attack on TWINE
block cipher with 80-bit secret key and also present the improved version of the work done by
Jongsung et al. in on DES.We focus on TWINE-80 security when the rst 7, 8 and 9-rounds
of the cipher are masked. Our 7-masked round attack requires the lowest measurements (222:58)
and can recover 12-bits of the secret key. In our 8-masked round attack, we can nd 24-bits of
the secret key with 232:58 measurements whereas in our 9-masked round attack, we are able to
nd 40-bits of the secret key information with 246:17 measurements. The fact that encryption
and decryption functions of TWINE-80 are similar can be utilized to launch the above attacks
when the last 7, 8 and 9 rounds of the cipher are masked. Thus, we show that at least 20 rounds
of TWINE-80 need to be masked to ensure security against side channel leakage. The differential
characteristics constructed to demonstrate our attacks are new and hitherto not been reported
before for TWINE-80.
In our work on DES, we improved the 7-round masked attack in using one more characteristic mentioned in and we recover full round 48-bit subkey of the rst round. The data
complexity of our attack is 236:99. The time complexity is 236:99 measurements and 235:99 curve
comparisons.