![]() Finally, salting means that it is impossible to determine whether two users have the same password without cracking the hashes, as the different salts will result in different hashes even if the passwords are the same. Salting also protects against an attacker pre-computing hashes using rainbow tables or database-based lookups. This makes cracking large numbers of hashes significantly harder, as the time required grows in direct proportion to the number of hashes. As the salt is unique for every user, an attacker has to crack hashes one at a time using the respective salt rather than calculating a hash once and comparing it against every stored hash. Password Storage Concepts ¶ Salting ¶Ī salt is a unique, randomly generated string that is added to each password as part of the hashing process. It is your responsibility as an application owner to select a modern hashing algorithm. Strong passwords stored with modern hashing algorithms and using hashing best practices should be effectively impossible for an attacker to crack. While the number of permutations can be enormous, with high speed hardware (such as GPUs) and cloud services with many servers for rent, the cost to an attacker is relatively small to do successful password cracking especially when best practices for hashing are not followed. Dictionaries or wordlists of common passwords.Brute force (trying every possible candidate).Lists of passwords obtained from other compromised sites.Different methods can be used to select candidate passwords, including: This process is repeated for a large number of potential candidate passwords. If they match, you have correctly "cracked" the hash and now know the plaintext value of their password. Compare the hash you calculated to the hash of the victim.Select a password you think the victim has chosen (e.g.How Attackers Crack Password Hashes ¶Īlthough it is not possible to "decrypt" password hashes to obtain the original passwords, it is possible to "crack" the hashes in some circumstances. Where possible, an alternative architecture should be used to avoid the need to store passwords in an encrypted form.įor further guidance on encryption, see the Cryptographic Storage Cheat Sheet. This might be necessary if the application needs to use the password to authenticate with another system that does not support a modern way to programmatically grant access, such as OpenID Connect (OIDC). In the context of password storage, encryption should only be used in edge cases where it is necessary to obtain the original plaintext password. Hashing their address would result in a garbled mess. Encryption is appropriate for storing data such as a user's address since this data is displayed in plaintext on the user's profile. Even if an attacker obtains the hashed password, they cannot enter it into an application's password field and log in as the victim.Įncryption is a two-way function, meaning that the original plaintext can be retrieved. Hashing is appropriate for password validation. Hashing is a one-way function (i.e., it is impossible to "decrypt" a hash and obtain the original plaintext value). However, in almost all circumstances, passwords should be hashed, NOT encrypted. ![]() Hashing and encryption both provide ways to keep sensitive data safe. Consider using a pepper to provide additional defense in depth (though alone, it provides no additional secure characteristics).If FIPS-140 compliance is required, use PBKDF2 with a work factor of 600,000 or more and set with an internal hash function of HMAC-SHA-256. ![]()
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