卓澤朋,崇金鳳,王 慧
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三類布爾函數(shù)的相關(guān)函數(shù)研究
卓澤朋,崇金鳳,王 慧
(淮北師范大學(xué)數(shù)學(xué)科學(xué)學(xué)院,安徽 淮北 235000)
布爾函數(shù);Bent函數(shù);自相關(guān)函數(shù);非線性度;全局雪崩準(zhǔn)則;絕對(duì)值指標(biāo)
Bent函數(shù)[1]是非線性度達(dá)到最大的一類布爾函數(shù),在密碼設(shè)計(jì)和通信領(lǐng)域有著廣泛應(yīng)用。但該類函數(shù)也有弱點(diǎn),如沒有彈性,只能是偶數(shù)維的函數(shù)。為了彌補(bǔ)Bent函數(shù)的不足,又相繼提出了部分Bent函數(shù)[2]、半-Bent函數(shù)[3]和Plateaued函數(shù)[4]等。嚴(yán)格雪崩準(zhǔn)則(Strict Avalanche Criterion, SAC)[5]和擴(kuò)散準(zhǔn)則(Propagation Criterion, PC)[6]研究的是布爾函數(shù)與其移位布爾函數(shù)的相關(guān)程度,但它們只對(duì)某些點(diǎn)的自相關(guān)值有要求,而對(duì)其他點(diǎn)不加限制,這會(huì)導(dǎo)致布爾函數(shù)安全的局部性。為了克服這方面的缺點(diǎn)和不足,文獻(xiàn)[7]提出布爾函數(shù)的全局雪崩準(zhǔn)則(Global Avalanche Criterion, GAC),并引入與之相關(guān)的2個(gè)指標(biāo):絕對(duì)值指標(biāo)和平方和指標(biāo),研究表明,這2個(gè)指標(biāo)越小,布爾函數(shù)的GAC越好,Bent函數(shù)恰好能達(dá)到這2個(gè)指標(biāo)的下界。GAC從全局出發(fā),對(duì)所有點(diǎn)提出了要求,使人們對(duì)SAC和PC有了進(jìn)一步思考[7-8]。文獻(xiàn)[9]討論2個(gè)布爾函數(shù)間的GAC,將一個(gè)布爾函數(shù)的GAC推廣到2個(gè)不同布爾函數(shù)之間,得到2個(gè)不同布爾函數(shù)GAC的上下界,對(duì)文獻(xiàn)[7]中的結(jié)果進(jìn)行了推廣。在文獻(xiàn)[10-12]中,研究了任意4個(gè)布爾函數(shù)的互相關(guān)函數(shù)間滿足的一個(gè)等式,利用該等式得到很多結(jié)論。
首先給出一些符號(hào)說明:
從互相關(guān)函數(shù)的定義很容易得到:
Bent函數(shù)恰好能達(dá)到這2個(gè)指標(biāo)的下界,這2個(gè)指標(biāo)越小,布爾函數(shù)的GAC越好。
由自相關(guān)函數(shù)的定義得到:
結(jié)論得證。
布爾函數(shù)的相關(guān)函數(shù)能刻畫布爾函數(shù)的擴(kuò)散特征和線性結(jié)構(gòu)特征,在布爾函數(shù)的性質(zhì)研究中發(fā)揮著重要作用,利用互相關(guān)函數(shù)的定義得到:
證明:根據(jù)互相關(guān)函數(shù)的定義,有:
結(jié)論得證。
注:在定理2中:
在文獻(xiàn)[22]中,利用此等式給出了任意三次布爾函數(shù)的自相關(guān)函數(shù)平方的上界,借助該上界進(jìn)一步研究了多類重要的跡函數(shù)表示的三次布爾函數(shù)的平方和指標(biāo)與絕對(duì)值指標(biāo)的上下界問題。將該上界敘述如下:
所以:
因此,根據(jù)引理得到:
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編輯 陸燕菲
Research on Correlation Function for Three Classes of Boolean Functions
ZHUO Ze-peng, CHONG Jin-feng, WANG Hui
(School of Mathematical Science, Huaibei Normal University, Huaibei 235000, China)
Boolean function; Bent function; auto-correlation function; degree of nonlinearity; Global Avalanche Criterion(GAC);absolute value indicator
1000-3428(2014)03-0180-04
A
TN918.1
安徽省自然科學(xué)基金資助項(xiàng)目(1208085QF119);安徽高校省級(jí)自然科學(xué)研究基金資助項(xiàng)目(KJ2012Z353, KJ2013Z286)。
卓澤朋(1978-),男,副教授、博士,主研方向:密碼學(xué),信息安全;崇金鳳,副教授、碩士;王 慧,講師、碩士。
2013-01-14
2013-03-18 E-mail:zepengzhu@chnu.edu.cn
10.3969/j.issn.1000-3428.2014.03.037