Topic: password protection

topics > computer science > Group: security

database security
one-way hash function
operating system security
security by capabilities


Password controlled access is frequently used in multi-user systems, but it works only as long as the passwords are kept secret. Password protection methods include: non-echoed password entry, long delays on repeated password attempts, encrypted password files with user and system components, password review eliminating poor choices, and equivalent system response for all access failures. The purpose of passwords is user identification. The same function can be served by: magnetic identification cards, speech recognition, handwriting recognition, and hardware signatures. (cbb 5/80)
Subtopic: password up

Quote: passwords should also provide mutual authentication, authenticated key exchange, and user identity protection [»haleS8_1999]
Quote: if the porter only admits people with invitations, we trust that admitted people have an invitation [»lost entries]

Subtopic: good password up

Quote: good passwords: word pairs with punctuation, pass phrase; avoid letter permutations; use proactive password checking
Quote: a pass phrase is a 5-10 word English phrase used as a password [»feldDC8_1989]

Subtopic: written password up

Quote: use a two part password, a long password on a slip of paper and a short one memorized [»schnB_2000]
Quote: one-time passwords written down as a list; store the list securely [»schnB_2000]

Subtopic: alternative passwords up

Quote: for a password a knitter might knit-and-purl 25 stitches; safe even from most onlookers [»haskJA8_1984]
Quote: pass-algorithms: instead of a password, let the computer present and manipulate data while the user remembers an algorithm [»haskJA8_1984]
Quote: a pass-algorithm could embed the subpassword data somewhere in the prompt [»haskJA8_1984]

Subtopic: security agent up

Quote: the Plan 9 factotum handles the user's keys and security interactions; no cryptographic code in applications; like the SSH agent [»coxR8_2002]
Quote: require an interactive dialog before unlocking personal accounts; protects against host-resident attacks [»coxR8_2002]
Quote: can attack Plan 9's factotum by rebooting the server with a debugging kernel [»coxR8_2002]

Subtopic: authentication server up

Quote: authentication server can prevent password guessing attack; allows memorizable password [»haleS8_1999]
Quote: all strong password mechanisms use public-key techniques to resist password-guessing attacks; probably necessary [»haleS8_1999]

Subtopic: call-back up

Quote: a call-back, prevents a site from masquerading as another site [»nowiDA8_1978]

Subtopic: nonce and salt up

Quote: UNIX uses encrypted passwords that include a random number assigned by the system to the user [»morrR11_1979, OK]
Quote: UNIX prevents key searching by encrypting password with a 12-bit random salt; so 4096 versions of each password [»morrR4_1978]

Subtopic: hardware password up

Quote: the Telecomputer includes a secret, built-in password as well as a user password [»morgC4_1982]

Subtopic: password file up

Quote: UNIX first used a cleartext password file with strong access protection; vulnerable when editing; lapse revealed all passwords [»morrR4_1978]

Subtopic: challenge-response up

Quote: an intruder can replace the login command and capture passwords; avoid by challenge-response or a handheld authenticator [»bellSM10_1990]

Subtopic: bad passwords up

Quote: nearly all cryptographic failures due to protocol or password deficiences; e.g., using nine random characters to protect PGP's private keys [»lensAK9_2001]
Quote: even in the CIA, only 85% of passwords are good [»zippJ6_2001]
Quote: in a week, identified 21% of the passwords from 15,000 accounts [»kleiDV5_1991]
Quote: on an unsecured system, can guess over 30% of the passwords by running large word lists through the crypt function [»feldDC8_1989]

Subtopic: password searches up

Quote: conventional passwords are easily attacked: exhaustive search, guessing, dictionary, capturing unencrypted passwords, trapdoors, etc. [»neumPG4_1994]
Quote: performance of crypt password authentication increased from 4 per second in 1976 to 200,000 per second in 1999
Quote: UNIX password system for frustrating widespread password searches; super-user passwords already effective [»morrR4_1978]
Quote: crypts/sec/dollar has improved 10^5x in 10 years; need to increase password entropy to improve password security [»feldDC8_1989]
Quote: can exhaustively search passwords of 7-8 lower-case letters; if improvement repeats, will need 8 full-ASCII passwords in 10 years [»feldDC8_1989]
Quote: a precomputed password dictionary is 28x faster than real-time encryption [»feldDC8_1989]

Subtopic: preventing attacks up

Quote: use bcrypt and eksblowfish for adaptable cost encryption and password authentication [»provN6_1999]
Quote: password algorithm should not be faster outside of normal use; fast CPU instructions, no bit transposition, no pipelining, no precomputation [»provN6_1999]
Quote: it is important to change passwords because increasing the time available for cracking requires increased password entropy [»feldDC8_1989]
Quote: to avoid hardware DES attacks, UNIX randomly changes the E-table of the DES algorithm [»morrR4_1978]
Quote: use exponential key exchange to limit password-guessing assaults [»bellSM10_1990]
Quote: use two passwords; the 2nd one closes the account if too many errors; prevents exhaustive search and sabotage of service [»morsD1_1986]
Quote: the response to an invalid login should be identical to that for a valid one [»morrR11_1979]
Quote: defeat password guessing with a hash function that has numerous collisions for the correct data and only one checksum for modified data; change password whenever the data changes or an attack is detected [»lomaM1_1995]

Subtopic: limitations of passwords up

Quote: passwords and security audits are no more than "security blankets" as long as hardware and software are vulnerable [»kargPA6_1974]
Quote: passwords are hard to maintain and reduce productivity; better to use short passwords that change yearly [»zippJ6_2001]
Quote: in Kerberos, all privileges depend ultimately on the user's typed password [»bellSM10_1990]
Quote: if a password system runs on a multi-user workstation, cached keys are accessible to attackers [»bellSM10_1990]
Quote: Unix password files do not authenticate the system to the user [»satyM8_1989]
Quote: Unix password files assumes physically secure communication

Related Topics up

Topic: authentication (93 items)
Topic: database security (12 items)
Topic: encryption (45 items)
Topic: one-way hash function (24 items)
Topic: operating system security (18 items)
Topic: security by capabilities
(65 items)

Updated barberCB 6/05
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Thesa is a trademark of C. Bradford Barber.