A modification of the Hill cipher algorithm was recently proposed by Ismail et al.(2006),who claimed that their new scheme could offer more security than the original one due to an extra non-linearity layer introduced...A modification of the Hill cipher algorithm was recently proposed by Ismail et al.(2006),who claimed that their new scheme could offer more security than the original one due to an extra non-linearity layer introduced via an elaborated key gen-eration mechanism.That mechanism produces one different encryption key for each one of the plaintext blocks.Nevertheless,we show in this paper that their method still has severe security flaws whose weaknesses are essentially the same as that already found in the original Hill cipher scheme.展开更多
This paper studies the security of an image encryption scheme based on the Hill cipher (Ismail et al., 2006) and reports its following problems: (1) There is a simple necessary and sufficient condition that makes a nu...This paper studies the security of an image encryption scheme based on the Hill cipher (Ismail et al., 2006) and reports its following problems: (1) There is a simple necessary and sufficient condition that makes a number of secret keys invalid; (2) It is insensitive to the change of the secret key; (3) It is insensitive to the change of the plain-image; (4) It can be broken with only one known/chosen plaintext; (5) It has some other minor defects. The proposed cryptanalysis discourages any use of the scheme in practice.展开更多
To investigate the impact of antenna correlation on secrecy performance in MIMO wiretap channels with Nakagami-m fading, the expressions of secrecy outage probability and positive secrecy probability were derived. Div...To investigate the impact of antenna correlation on secrecy performance in MIMO wiretap channels with Nakagami-m fading, the expressions of secrecy outage probability and positive secrecy probability were derived. Diversity order and array gain were also achieved for further insight. The study was based on the information theory that physical layer security can be guaranteed when the quality of the main channel is higher than that of the eavesdropper's channel. Monte Carlo simulations well validated the numerical results of analytic expressions. It was shown that antenna correlation is detrimental to secrecy performance when average SNR of the main channel is at medium and high level. Interestingly, when average SNR of the main channel reduces to low level, the effect of antenna correlation becomes benefi cial to secrecy performance.展开更多
Temporal key integrity protocol （TKIP） is a sub-protocol of IEEE 802.11i. TKIP remedies some security flaws in wired equivalent privacy （WEP） protocol. TKIP adds four new algorithms to WEP： a message integrity co...Temporal key integrity protocol （TKIP） is a sub-protocol of IEEE 802.11i. TKIP remedies some security flaws in wired equivalent privacy （WEP） protocol. TKIP adds four new algorithms to WEP： a message integrity code （MIC） called Michael, an initialization vector （IV） sequencing discipline, a key mixing function and a reeying mechanism. The key mixing function, also called temporal key hash, de-correlates the IVs from weak keys. Some cryptographic properties of the substitution box （S-box） used in the key mixing function are investigated in this paper, such as regularity, avalanche effect, differ uniform and linear structure. Moen et al pointed out that there existed a temporal key recovery attack in TKIP key mixing function. In this paper a method is proposed to defend against the attack, and the resulting effect on performance is discussed.展开更多
文摘A modification of the Hill cipher algorithm was recently proposed by Ismail et al.(2006),who claimed that their new scheme could offer more security than the original one due to an extra non-linearity layer introduced via an elaborated key gen-eration mechanism.That mechanism produces one different encryption key for each one of the plaintext blocks.Nevertheless,we show in this paper that their method still has severe security flaws whose weaknesses are essentially the same as that already found in the original Hill cipher scheme.
基金the National Basic Research Program of China(No. 2006CB303104)the City University of Hong Kong under theSRG Project, China (No. 7002134)
文摘This paper studies the security of an image encryption scheme based on the Hill cipher (Ismail et al., 2006) and reports its following problems: (1) There is a simple necessary and sufficient condition that makes a number of secret keys invalid; (2) It is insensitive to the change of the secret key; (3) It is insensitive to the change of the plain-image; (4) It can be broken with only one known/chosen plaintext; (5) It has some other minor defects. The proposed cryptanalysis discourages any use of the scheme in practice.
文摘To investigate the impact of antenna correlation on secrecy performance in MIMO wiretap channels with Nakagami-m fading, the expressions of secrecy outage probability and positive secrecy probability were derived. Diversity order and array gain were also achieved for further insight. The study was based on the information theory that physical layer security can be guaranteed when the quality of the main channel is higher than that of the eavesdropper's channel. Monte Carlo simulations well validated the numerical results of analytic expressions. It was shown that antenna correlation is detrimental to secrecy performance when average SNR of the main channel is at medium and high level. Interestingly, when average SNR of the main channel reduces to low level, the effect of antenna correlation becomes benefi cial to secrecy performance.
基金the National Laboratory for Modern Communications(No.51436050304JW0317)the National Natural Science Foundation of China(No.60573030)
文摘Temporal key integrity protocol （TKIP） is a sub-protocol of IEEE 802.11i. TKIP remedies some security flaws in wired equivalent privacy （WEP） protocol. TKIP adds four new algorithms to WEP： a message integrity code （MIC） called Michael, an initialization vector （IV） sequencing discipline, a key mixing function and a reeying mechanism. The key mixing function, also called temporal key hash, de-correlates the IVs from weak keys. Some cryptographic properties of the substitution box （S-box） used in the key mixing function are investigated in this paper, such as regularity, avalanche effect, differ uniform and linear structure. Moen et al pointed out that there existed a temporal key recovery attack in TKIP key mixing function. In this paper a method is proposed to defend against the attack, and the resulting effect on performance is discussed.
