In cryptanalysis and computer security, a dictionary attack is an attack using a restricted subset of a keyspace to defeat a cipher or authentication mechanism by trying to determine its decryption key or passphrase, sometimes trying thousands or millions of likely possibilities[1] often obtained from lists of past security breaches.
A dictionary attack is based on trying all the strings in a pre-arranged listing. Such attacks originally used words found in a dictionary (hence the phrase dictionary attack);[2] however, now there are much larger lists available on the open Internet containing hundreds of millions of passwords recovered from past data breaches.[3] There is also cracking software that can use such lists and produce common variations, such as substituting numbers for similar-looking letters. A dictionary attack tries only those possibilities which are deemed most likely to succeed. Dictionary attacks often succeed because many people have a tendency to choose short passwords that are ordinary words or common passwords; or variants obtained, for example, by appending a digit or punctuation character. Dictionary attacks are often successful, since many commonly used password creation techniques are covered by the available lists, combined with cracking software pattern generation. A safer approach is to randomly generate a long password (15 letters or more) or a multiword passphrase, using a password manager program or manually typing a password.
It is possible to achieve a time–space tradeoff by pre-computing a list of hashes of dictionary words and storing these in a database using the hash as the key. This requires a considerable amount of preparation time, but this allows the actual attack to be executed faster. The storage requirements for the pre-computed tables were once a major cost, but now they are less of an issue because of the low cost of disk storage. Pre-computed dictionary attacks are particularly effective when a large number of passwords are to be cracked. The pre-computed dictionary needs be generated only once, and when it is completed, password hashes can be looked up almost instantly at any time to find the corresponding password. A more refined approach involves the use of rainbow tables, which reduce storage requirements at the cost of slightly longer lookup-times. SeeLM hash for an example of an authentication system compromised by such an attack.
Pre-computed dictionary attacks, or "rainbow table attacks", can be thwarted by the use of salt, a technique that forces the hash dictionary to be recomputed for each password sought, making precomputation infeasible, provided that the number of possible salt values is large enough.[4]
US Secret Service use a distributed dictionary attack on suspect's password protecting encryption keys
Testing for Brute Force (OWASP-AT-004) 2020-01-14 at the Wayback Machine
May 04, 2024
dictionary, attack, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, februar. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Dictionary attack news newspapers books scholar JSTOR February 2018 Learn how and when to remove this message In cryptanalysis and computer security a dictionary attack is an attack using a restricted subset of a keyspace to defeat a cipher or authentication mechanism by trying to determine its decryption key or passphrase sometimes trying thousands or millions of likely possibilities 1 often obtained from lists of past security breaches Contents 1 Technique 2 Pre computed dictionary attack Rainbow table attack 3 Dictionary attack software 4 See also 5 References 6 External linksTechnique editA dictionary attack is based on trying all the strings in a pre arranged listing Such attacks originally used words found in a dictionary hence the phrase dictionary attack 2 however now there are much larger lists available on the open Internet containing hundreds of millions of passwords recovered from past data breaches 3 There is also cracking software that can use such lists and produce common variations such as substituting numbers for similar looking letters A dictionary attack tries only those possibilities which are deemed most likely to succeed Dictionary attacks often succeed because many people have a tendency to choose short passwords that are ordinary words or common passwords or variants obtained for example by appending a digit or punctuation character Dictionary attacks are often successful since many commonly used password creation techniques are covered by the available lists combined with cracking software pattern generation A safer approach is to randomly generate a long password 15 letters or more or a multiword passphrase using a password manager program or manually typing a password Pre computed dictionary attack Rainbow table attack editIt is possible to achieve a time space tradeoff by pre computing a list of hashes of dictionary words and storing these in a database using the hash as the key This requires a considerable amount of preparation time but this allows the actual attack to be executed faster The storage requirements for the pre computed tables were once a major cost but now they are less of an issue because of the low cost of disk storage Pre computed dictionary attacks are particularly effective when a large number of passwords are to be cracked The pre computed dictionary needs be generated only once and when it is completed password hashes can be looked up almost instantly at any time to find the corresponding password A more refined approach involves the use of rainbow tables which reduce storage requirements at the cost of slightly longer lookup times See LM hash for an example of an authentication system compromised by such an attack Pre computed dictionary attacks or rainbow table attacks can be thwarted by the use of salt a technique that forces the hash dictionary to be recomputed for each password sought making precomputation infeasible provided that the number of possible salt values is large enough 4 Dictionary attack software editCain and Abel Crack Aircrack ng John the Ripper L0phtCrack Metasploit Project Ophcrack CryptoolSee also editBrute force attack E mail address harvesting Intercontinental Dictionary Series an online linguistic database Key derivation function Key stretching Password cracking Password strengthReferences edit Junghyun Nam Juryon Paik Hyun kyu Kang Ung Kim Dongho Won 2009 03 01 An off line dictionary attack on a simple three party key exchange protocol IEEE Communications Letters 13 3 205 207 doi 10 1109 LCOMM 2009 081609 ISSN 1089 7798 Jeff Atwood Dictionary Attacks 101 CrackStation s list e g with over 1 4 billion words CAPEC CAPEC 55 Rainbow Table Password Cracking Version 3 5 capec mitre org Retrieved 2021 09 12 External links editRFC 2828 Internet Security Glossary RFC 4949 Internet Security Glossary Version 2 US Secret Service use a distributed dictionary attack on suspect s password protecting encryption keys Testing for Brute Force OWASP AT 004 Archived 2020 01 14 at the Wayback Machine Retrieved from https en wikipedia org w index php title Dictionary attack amp oldid 1216526188, wikipedia, wiki, book, books, library,
