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What Is Password Authenticated Agreement

The third paragraph is “and then save only the chopped result”, but it should be “and then save only the chopped result and the salt” because the salt must be stored in plain text next to the password. I wrote a more in-depth blog post about the problems with using OPAQUE in web applications: This is a problem because the sub-purpose of SRP and OPAQUE is to prevent attackers from getting verifiers from the compromised server so that they can recover the original password easily or quickly. You can still get involved in brute force once you have verifiers, but the brute force attack should be as high as possible for the attacker. Augmented PAKE is a variant applicable to client/server scenarios where the server does not store data equivalent to a password. This means that an attacker who has stolen data from the server still cannot impersonate a client unless they first perform a brute force search for the password. Examples: The password-authenticated key agreement usually includes methods such as: This is a nice extension, I like it. However, you may have noticed that all serialization, storage, and transmission of messages is currently being moved to the application that uses this low-level library. However, it may be a good idea to provide a top-level API that hides all the unnecessary details and also provides services like what you offer to work on. The first password-authenticated key agreement methods were encrypted key exchange methods described in 1992 by Steven M. Bellovin and Michael Merritt. Although some of the initial methods were flawed, the surviving and improved forms of EKE effectively reinforce a shared password into a shared key that can then be used for message encryption and/or authentication. The first verifiably secure PAKE protocols were given in the work of M.

Bellare, D. Pointcheval and P. Rogaway (Eurocrypt 2000) and V. Boyko, P. MacKenzie and S. Patel (Eurocrypt 2000). These protocols proved safe in the so-called random oracle model (or even stronger variants), and the first protocols that proved safe under standard assumptions were those of O. Goldreich and Y. Lindell (Crypto 2001), which serve as proof of plausibility but are not effective, and J. Katz, R. Ostrovsky and M.

Yung (Eurocrypt 2001), which is convenient. A significant number of alternative and secure PAKE protocols have been developed as part of the work of M. Bellare, D. Pointcheval and P. Rogaway, variants and proofs of security have been proposed in this growing class of password-authenticated key tuning methods. The current standards for these methods are IETF RFC 2945, RFC 5054, RFC 5931, RFC 5998, RFC 6124, RFC 6617, RFC 6628 and RFC 6631, IEEE Std 1363.2-2008, ITU-T X.1035 and ISO-IEC 11770-4:2006. They leave the password hash on the client`s side, but they don`t feed it with the stored salt. Instead, they use a special two-part protocol called forgotten PRF to calculate a second salt (call it salt2) so that the client can use salt2 in the hash function – but doesn`t learn the original salt. An important feature is that a spy or man in the middle can`t get enough information to be able to guess a password without further interactions with the parties for every (few) guesses with brute force. This means that strong security can be achieved with weak passwords.

As with salt, why not just encrypt salt with symmetric encryption with a key derived from the user`s password? Balanced PAKE allows parties using the same password to negotiate and authenticate a common key. Examples of this: Sphinx (as reported by Krawczyk et al – same authors as opaque) in combination with opaque gives you very strong security guarantees, such as no offline dictionary attacks and also no proofreading attacks. It`s pretty cool and goes far beyond just hashing passwords. In addition, hash functions (whether MD5 or Argon2) always generate a token that can be reused in replay attacks such as pass-the-hash or simply sniff the password itself. In opaque, ephemeral keys also eliminate this. If the client wants to authenticate with the OPAQUE protocol, the server sends the stored C ciphertext to the client. If the client entered the correct password in the first phase, it can derive K and now decrypt this ciphertext. Otherwise, it is useless. With the built-in secret, it can now execute a standard authenticated key memorandum of understanding to complete the negotiation. (The server validates client input against its copy of the client`s public key, and the client does the same.) The basic idea of such a function is that the server and the client can jointly calculate a PRF function (salt, password), where the server knows “salt” and the client “password”. Only the client learns the output of this function.

Neither party learns from the other party`s contribution. The solution used by OPAQUE is based on an old idea of Gentry, Mackenzie and Ramzan. When the user first registers with the server, it generates a strong public and private key for a secure memorandum of understanding (such as HMQV) and encrypts the resulting private key under K with the server`s public key. The authenticated cipher text (and the resulting public key) is stored in the password database. When I started thinking about PEKEs a few months ago, I couldn`t help but notice that most of the existing work was a bit grumpy. Either it had strange problems like SRP, or it forced the user to store the password (or an effective password) on the server, or it revealed the salt to an attacker – allowing for pre-calculation attacks. actual_salt = decrypt(encrypted_salt, someKDF(password)) In cryptography, a password-authenticated key agreement method is an interactive method that allows two or more parties to create cryptographic keys based on one or more parties` knowledge of a password. This conversation is getting stranger and weirder. I have not denied that OPAQUE has a certain appeal. I`m just saying that it doesn`t offer any advantage in the specific web page scenario. Repeated attacks? To reproduce something, it would first have to be intercepted.

Which most likely means you could have manipulated the login page and simply stolen the password. No offline dictionary attacks? If I understood this correctly when analyzing the description, it requires an additional hardware token. Of course, with a hardware token, you can go beyond just hashing passwords. .