G. Purdy, A high-security log-in procedure, Communications of the ACM, 17 (1974), pp. 442-445.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....the secret key encryption function may be replaced by a keyed hash function [4] Another weakness of login protocols resides in the privacy of the password file. So, instead of storing passwords, system administrators usually store oneway functions of passwords in a write protected file [10, 16]. Therefore even if someone breaks into the computer and steals the password file, he cannot recover the passwords because of the one way function applied on the passwords. Unfortunately, the use of one way functions only partially solve the problem: the password file is still vulnerable to ....

G.P. Purdy. A high security log-in procedure. Communications of the ACM, 17(8):442--445, August 1974.

....as an encoding relation e = f(f(x) f (x) j f(x) 2 C ( 0; 1] g and integration as a decoding relation d = f(f(x) R x f(x)dx k) j f(x) 2 C( 0; 1] k 2 Rg, then we obtain a precode (P; C; e; d) The opposite (C; P; d; e) is a code. Example 4 The high security login a la Purdy [10] can be understood as a precode (P; C; e; where e is a publicly known one way function from the set of passwords P to enciphered words C. The decoding relation is by design void. The resulting precode is a code, since d e = is a subset of the identity relation on P . The high security ....

G.P. Purdy. A high-security log-in procedure. Comm. of the ACM, 17(4):442-445, 1974.

....a pair of codes of this one way encodeless type. The genetic code is similar, but less extreme. Its encode is empty, and its decode is a function. The code at left has an empty decode relation d = #, and an encode relation e which is a function. Clearly de = #. The Purdy high security login [9] is a code of this one way decodeless type. Other such examples are hash functions when viewed as one way objects. The code at left has an injective (i.e. one to one) encode relation e, and a decode relation d which is a function. Many error correcting codes are of this type. In particular, ....

G.P. Purdy. A high-security log-in procedure. Comm. of the ACM, 17(4):442--445, 1974.

....systems, users passwords are stored in a special file, which has the disadvantage that anyone who gets access to that file is able to freely impersonate any legitimate user. Therefore that file has to be specially protected by the operating system. It has been known for a long time (cf. [54]) that one can eliminate the need for any secrecy by eliminating the storage of passwords themselves. Instead, one utilizes a function f that is hard to invert (i.e. such that given a y in the range of f, it is hard to find an x in the domain of f such that f (x) y) and creates a file ....

G. B. Purdy, A high security log-in procedure, Comm. ACM 17 (1974), 442-445.

....the secret key encryption function may be replaced by a keyed hash function [4] Another weakness of login protocols resides in the privacy of the password file. So, instead of storing passwords, system administrators usually store oneway functions of passwords in a write protected file [10, 16]. Therefore even if someone breaks into the computer and steals the password file, he cannot recover the passwords because of the one way function applied on the passwords. Unfortunately, the use of one way functions only partially solve the problem: the password file is still vulnerable to ....

G.P. Purdy. A high security log-in procedure. Communications of the ACM, 17(8):442--445, August 1974.

....that somehow or other all messages entering and leaving every processor undergo a simple transformation that users cannot bypass. The transformation works like this. Each port is really a pair of ports, P, and G, related by: P = F (G ) where F is a (publicly known) one way function [Wilkes 1968; Purdy 1974; Evans et al. 1974] performed by the F box. The one way function has the property that given G it is a straightforward computation to find P, but that given P, finding G is not feasible. Using the one way F box, the server authentication can be handled in a simple way, as illustrated in Fig 1. ....

Purdy, G.B.: "A High-Security Log-in Procedure," Commun. ACM, vol. 17, pp. 442-445, Aug. 1974.

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G. Purdy, A high-security log-in procedure, Communications of the ACM, 17 (1974), pp. 442-445.

No context found.

G.P. Purdy. A high-security log-in procedure. Comm. of the ACM, 17(4):442--445, 1974.

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