使用輸入字串產生16x16動態盒

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Title:	使用輸入字串產生16x16動態盒
Other Titles:	Generating a 16x16 Dynamic Box by Employing Input String
Authors:	潘星佑 PAN, XING-YOU
Contributors:	黃宜豊 HUANG, YI-LI 資訊工程學系
Keywords:	S-Box;GDBIS;D-Box;AES;GDBRK;E-DASS S-Box;GDBIS;D-Box;AES;GDBRK;E-DASS
Date:	2018
Issue Date:	2019-01-10T09:04:17Z (UTC)
Abstract:	鑑於透過使用查表方式進行加密和解密資料非常快速且富變化，但是目前使用的表是靜態S-Box，其內容是固定且為大眾周知，秘密性大為降低，然而若能夠根據使用者輸入的密碼字串來重建表的內容，則此表將因不同的密碼而有不同的內容，呈現動態改變，攻擊者亦因不知道密碼而不知表的內容，安全度將大大提升。在本研究中，我們開發出一種演算法，即，使用輸入字串產生16x16動態盒(Generate a 16 x 16 Dynamic Box by using an Input String，簡稱GDBIS)，字串長度介於8位元到800000位元之間，可有效抵禦暴力法攻擊。GDBIS有三個程序，(1)產生初始循序密鑰ISK1和ISK2; (2)產生動態密鑰，DK1，DK2和DK3; (3)透過使用一種稱為Dynamic Box Generator（DBG for short）演算法產生動態盒(D-Box)。本研究同時開發了一種新的密鑰擴展演算法，稱為Generation of D-Box and Round Keys（GDBRK for short）。GDBRK由輸入的Cipher key 透過GDBIS演算法產生一個16x16 D-Box，再使用此D-Box產生Round Keys。此外，AES中使用的S-Box將被此D-Box取代如此將提高安全度而能保有效能。根據我們的安全分析，經由GDBIS產生的D-Box是不可逆轉的，具有高度的混亂與極高的輸入敏感度。而由GDBRK產生的Round Keys其相互間的關聯度極低。效能分析顯示，GDBIS用於產生D-Box的時間介於15到19μs之間，由於Cipher key 長度的不同GDBRK耗時介於20和25μs之間，表明這兩種機制具有出色的安全度與效能，能夠滿足實際應用的需要。 Today, encrypting and decrypting data by employing a lookup table is ever changeful and very quickly. But currently, the table to be looked up is a static S-Box, the contents of which is fixed, well-known and greatly reduced the confidentiality. However, if the contents of the table can be reconstructed according to the password input by the user, the table will have various contents due to different passwords. The attacker also does not know the contents of the table because he does not know the password, and thus, the security will be greatly improved. Based on this, in this study, we propose an algorithm, namely Generate a 16 x 16 Dynamic Box by using an Input String (GDBIS for short). The length of the password string is between 8 bits and 800,000 bits, which can effectively defend against all kinds of brute-force attack. The GDBIS has three procedures, including the one that generates Initial Serial Keys, ISK1 and ISK2; the one that produces Dynamic Keys, DK1, DK2 and DK3; the procedure that yields a D-Box by using an algorithm, named Dynamic Box Generator (DBG for short). We also develop a new key expansion algorithm, called Generation of D-Box and Round Keys (GDBRK for short). Given a Cipher key, the GDBRK generates a D-Box, with which to produce Round Keys sequentially. The S-Box used in AES is also substituted by the D-Box for further increasing its security level without the loss of its encryption and decryption performance. According to our security analysis, the D-Box generated by GDBIS is irreversible with high degree of chaos and has excellent sensitivity on inputs. The Round Keys generated by the GDBRK have low relation among themselves. Our performance analysis also shows that the time that the GDBIS spends to generate a D-Box are between 15 and 19 μs. Due to the difference in password length, GDBRK takes between 20 and 25μs showing that the two mechanisms have excellent performance and are able to meet the needs of practical applications.
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