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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.
Technique
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.
Pre-computed dictionary attack/Rainbow table attack
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. 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
See also
- Brute-force attack
- E-mail address harvesting
- Intercontinental Dictionary Series, an online linguistic database
- Key derivation function
- Key stretching
- Password cracking
- Password strength
References
- ^ 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
- RFC 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
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Cryptanalysis
Computer security
Cipher
Passphrase
Leet
Passphrase
Password manager
Time–space tradeoff
Pre-computing
Cryptographic hash function
Unique key
Disk storage
Rainbow table
LM hash
Authentication protocol
Salt (cryptography)
Precomputation
Cain and Abel (software)
Crack (password software)
Aircrack-ng
John the Ripper
L0phtCrack
Metasploit Project
Ophcrack
Cryptool
Brute-force attack
Intercontinental Dictionary Series
Key derivation function
Key stretching
Password cracking
Password strength
Doi (identifier)
ISSN (identifier)
Wayback Machine
Dictionary attack
Dictionary attack
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هجوم المعجم
Atac de diccionari
Slovníkový útok
Ordbogsangreb
Wörterbuchangriff
Ataque de diccionario
حمله لغتنامهای
Attaque par dictionnaire
사전 공격
Attacco a dizionario
Attacch a dizionari
നിഘണ്ടു ആക്രമണം
Толь бичгийн халдлага
Woordenlijstaanval
辞書攻撃
Ordbokangrep
ਡਿਕਸ਼ਨਰੀ ਅਟੈਕ
Atak słownikowy
Ataque de dicionário
Перебор по словарю
Dictionary attack
Ordboksattack
การโจมตีด้วยคำจากพจนานุกรม
Перебір за словником
Tấn công từ điển
字典攻擊
Special:EntityPage/Q599809#sitelinks-wikipedia
Dictionary attack
Talk:Dictionary attack
Dictionary attack
Dictionary attack
Special:WhatLinksHere/Dictionary attack
Special:RecentChangesLinked/Dictionary attack
Wikipedia:File Upload Wizard
Special:SpecialPages
Special:EntityPage/Q599809
Dictionary attack
Dictionary attack
Main Page
Wikipedia:Contents
Portal:Current events
Special:Random
Wikipedia:About
Wikipedia:Contact us
Special:FundraiserRedirector?utm source=donate&utm medium=sidebar&utm campaign=C13 en.wikipedia.org&uselang=en
Help:Contents
Help:Introduction
Wikipedia:Community portal
Special:RecentChanges
Wikipedia:File upload wizard
Main Page
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Help:Introduction
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Special:MyTalk
هجوم المعجم
Atac de diccionari
Slovníkový útok
Ordbogsangreb
Wörterbuchangriff
Ataque de diccionario
حمله لغتنامهای
Attaque par dictionnaire
사전 공격
Attacco a dizionario
Attacch a dizionari
നിഘണ്ടു ആക്രമണം
Толь бичгийн халдлага
Woordenlijstaanval
辞書攻撃
Ordbokangrep
ਡਿਕਸ਼ਨਰੀ ਅਟੈਕ
Atak słownikowy
Ataque de dicionário
Перебор по словарю
Dictionary attack
Ordboksattack
การโจมตีด้วยคำจากพจนานุกรม
Перебір за словником
Tấn công từ điển
字典攻擊
Special:EntityPage/Q599809#sitelinks-wikipedia
Dictionary attack
Talk:Dictionary attack
Dictionary attack
Dictionary attack
Special:WhatLinksHere/Dictionary attack
Special:RecentChangesLinked/Dictionary attack
Wikipedia:File Upload Wizard
Special:SpecialPages
Special:EntityPage/Q599809
Dictionary attack
Dictionary attack
Main Page
Wikipedia:Contents
Portal:Current events
Special:Random
Wikipedia:About
Wikipedia:Contact us
Special:FundraiserRedirector?utm source=donate&utm medium=sidebar&utm campaign=C13 en.wikipedia.org&uselang=en
Help:Contents
Help:Introduction
Wikipedia:Community portal
Special:RecentChanges
Wikipedia:File upload wizard
Main Page
Special:Search
Help:Introduction
Special:MyContributions
Special:MyTalk
هجوم المعجم
Atac de diccionari
Slovníkový útok
Ordbogsangreb
Wörterbuchangriff
Ataque de diccionario
حمله لغتنامهای
Attaque par dictionnaire
사전 공격
Attacco a dizionario
Attacch a dizionari
നിഘണ്ടു ആക്രമണം
Толь бичгийн халдлага
Woordenlijstaanval
辞書攻撃
Ordbokangrep
ਡਿਕਸ਼ਨਰੀ ਅਟੈਕ
Atak słownikowy
Ataque de dicionário
Перебор по словарю
Dictionary attack
Ordboksattack
การโจมตีด้วยคำจากพจนานุกรม
Перебір за словником
Tấn công từ điển
字典攻擊
Special:EntityPage/Q599809#sitelinks-wikipedia
Dictionary attack
Talk:Dictionary attack
Dictionary attack
Dictionary attack
Special:WhatLinksHere/Dictionary attack
Special:RecentChangesLinked/Dictionary attack
Wikipedia:File Upload Wizard
Special:SpecialPages
Special:EntityPage/Q599809
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