Showing papers on "Rainbow table published in 2012"

CPHASH: a cache-partitioned hash table

Abstract: CPHash is a concurrent hash table for multicore processors. CPHash partitions its table across the caches of cores and uses message passing to transfer lookups/inserts to a partition. CPHash's message passing avoids the need for locks, pipelines batches of asynchronous messages, and packs multiple messages into a single cache line transfer. Experiments on a 80-core machine with 2 hardware threads per core show that CPHash has ~1.6x higher throughput than a hash table implemented using fine-grained locks. An analysis shows that CPHash wins because it experiences fewer cache misses and its cache misses are less expensive, because of less contention for the on-chip interconnect and DRAM. CPServer, a key/value cache server using CPHash, achieves ~5% higher throughput than a key/value cache server that uses a hash table with fine-grained locks, but both achieve better throughput and scalability than memcached. The throughput of CPHash and CPServer also scale near-linearly with the number of cores.

Building an Efficient Hash Table on the GPU

Abstract: Publisher Summary This chapter describes a straightforward algorithm for parallel hash table construction on the graphical processing unit (GPU). It constructs the table in global memory and use atomic operations to detect and resolve collisions. Construction and retrieval performance are limited almost entirely by the time required for these uncoalesced memory accesses, which are linear in the total number of accesses; so the design goal is to minimize the average number of accesses per insertion or lookup. In fact, it guarantees a constant worst-case bound on the number of accesses per lookup. Further, one alternative to using a hash table is to store the data in a sorted array and access it via binary search. Sorted arrays can be built very quickly using radix sort because the memory access pattern of radix sort is very localized, allowing the GPU to coalesce many memory accesses and reduce their cost significantly. However, binary search, which incurs as many as lg ( N) probes in the worst case, is much less efficient than hash table lookup. GPU hash tables are useful for interactive graphics applications, where they are used to store sparse spatial data—usually 3D models that are voxelized on a uniform grid. Rather than store the entire voxel grid, which is mostly empty, a hash table is built to hold just the occupied voxels.

Breaking the GSM A5/1 cryptography algorithm with rainbow tables and high-end FPGAS

Abstract: A5 is the basic cryptographic algorithm used in GSM cell-phones to ensure that the user communication is protected against illicit acts. The A5/1 version was developed in 1987 and has since been under attack. The most recent attack on A5/1 is the “A51 security project”, led by Karsten Nohl that consists of the creation of rainbow tables that map the internal state of the algorithm with the keystream. Rainbow tables are efficient structures that allow the tradeoff between run-time (computations performed to crack a conversation) and space (memory to hold pre-computed information). In this paper we describe a very effective parallel architecture for the creation of the A5/1 rainbow tables in reconfigurable hardware. Rainbow table creation is the most expensive portion of cracking a particular encrypted information exchange. Our approach achieves almost 3000× speedup over a single processor, and 2.5× speedup compared to GPUs. This performance is achieved with less than 5 Watt power consumption, achieving an energy efficiency in the order of 150x better that the GPU approach.

Security Analysis of salt||password Hashes

Abstract: Protection of passwords used to authenticate computer systems and networks is one of the most important application of cryptographic hash functions. Due to the application of precomputed memory look up attacks such as birthday and dictionary attacks on the hash values of passwords to find passwords, it is usually recommended to apply hash function to the combination of both the salt and password, denoted salt||password, to prevent these attacks. In this paper, we present the first security analysis of salt||password hashing application. We show that when hash functions based on the compression functions with easily found fixed points are used to compute the salt||password hashes, these hashes are susceptible to precomputed offline birthday attacks. For example, this attack is applicable to the salt||password hashes computed using the standard hash functions such as MD5, SHA-1, SHA-256 and SHA-512 that are based on the popular Davies-Meyer compression function. This attack exposes a subtle property of this application that although the provision of salt prevents an attacker from finding passwords, salts prefixed to the passwords do not prevent an attacker from doing a precomputed birthday attack to forge an unknown password. In this forgery attack, we demonstrate the possibility of building multiple passwords for an unknown password for the same hash value and salt. Interestingly, password||salt (i.e. salts suffixed to the passwords) hashes computed using Davies-Meyer hash functions are not susceptible to this attack, showing the first security gap between the prefix-salt and suffix-salt methods of hashing passwords.

LightFlow: Speeding up GPU-based flow switching and facilitating maintenance of flow table

Abstract: Flow-based switching is increasingly important in accordance with the growing demand for in-network processing for cloud applications. Flow switching performance tends to be degraded in proportion to the number of flow entries. To reduce the number of flow entries, they can be aggregated by applying wildcard fields. Meanwhile, the existence of the wildcard entry adversely affects the use of a hash-based lookup on a flow table, and thus a linear search is inherent in flow switching. However, the linear search is currently the primary cause of performance limitation. To date, two flow tables, one for hash-based lookup and the other for a wildcard-enabled linear search, have been used for flow switching. While hash-based table lookup is much faster than linear search, it needs to be manually updated for every exact match entry. Maintaining a hash-based table of all the flow switches is not feasible from a network operator viewpoint. In this paper, LightFlow, a mechanism to accelerate software flow switching processing and relieve the burden of maintaining the flow table is proposed. In LightFlow, two-dimensional parallelization of a linear search is introduced to accelerate lookup of the wildcard-enabled flow entries. It also introduces a mechanism that allows updating of the hash table to be performed automatically based on the result of wildcardaware table lookup. LightFlow satisfies both the need for fast table lookup and feasibility of flow table management which needs to allow a large number of wildcard entries. Experimental results show that LightFlow can increase the speed of lookup of a wildcard-aware flow table three-fold or more compared to the current GPU-based wildcard search mechanisms.

Flow key lookup involving multiple simultaneous cam operations to identify hash values in a hash bucket

Abstract: A flow key is determined from an incoming packet. Two hash values A and B are then generated from the flow key. Hash value A is an index into a hash table to identify a hash bucket. Multiple simultaneous CAM lookup operations are performed on fields of the bucket to determine which ones of the fields store hash value B. For each populated field there is a corresponding entry in a key table and in other tables. The key table entry corresponding to each field that stores hash value B is checked to determine if that key table entry stores the original flow key. When the key table entry that stores the original flow key is identified, then the corresponding entries in the other tables are determined to be a “lookup output information value”. This value indicates how the packet is to be handled/forwarded by the network appliance.

Low-Overhead Enhancement of Reliability of Journaled File System Using Solid State Storage and De-Duplication

Abstract: A mechanism is provided in a data processing system for reliable asynchronous solid-state device based de-duplication. Responsive to receiving a write request to write data to the file system, the mechanism sends the write request to the file system, and in parallel, computes a hash key for the write data. The mechanism looks up the hash key in a de-duplication table. The de-duplication table is stored in a memory or a solid-state storage device. Responsive to the hash key not existing in the de-duplication table, the mechanism writes the write data to a storage device, writes a journal transaction comprising the hash key, and updates the de-duplication table to reference the write data in the storage device.

A Comparison of Perfect Table Cryptanalytic Tradeoff Algorithms.

Abstract: The performances of three major time memory tradeoff algorithms were compared in a recent paper. The algorithms considered there were the classical Hellman tradeoff and the non-perfect table versions of the distinguished point method and the rainbow table method. This paper adds the perfect table versions of the distinguished point method and the rainbow table method to the list, so that all the major tradeoff algorithms may now be compared against each other. Even though there are existing claims as to the superiority of one tradeoff algorithm over another algorithm, the algorithm performance comparisons provided by the current work and the recent preceding paper are of more practical value. Comparisons that take both the cost of pre-computation and the efficiency of the online phase into account, at parameters that achieve a common success rate, can now be carried out with ease. Comparisons can be based on the expected execution complexities rather than the worst case complexities, and details such as the effects of false alarms and various storage optimization techniques need no longer be ignored. A significant portion of this paper is allocated to accurately analyzing the execution behavior of the perfect table distinguished point method. In particular, we obtain a closed-form formula for the average length of chains associated with a perfect distinguished point table.

A Reliable Dynamic User-Remote Password Authentication Scheme over Insecure Network

Abstract: Protocols of user authentication are able to ensure the security of data transmission and usersi¦ communication over insecure networks. Among various authenticated mechanisms run currently, the password-based user authentication, because of its efficiency, is the most widely employed in different areas, such as computer networks, wireless networks, remote login, operation systems, and database management systems. Even as password is endowed with the property of simple and human memorable, for which causes such an attack of brute force, for example, the previous works often suffer off-line password guessing attack. Therefore, an ameliorative password-based authentication scheme is proposed in this paper, achieving to resist off-line password guessing attacks, replay attacks, on-line password guessing attacks, and ID-theft attacks. In light of security, the proposed scheme is provided with good practicability, even over insecure network.

How to break EAP-MD5

Abstract: We propose an efficient attack to recover the passwords, used to authenticate the peer by EAP-MD5, in the IEEE 802.1X network. First, we recover the length of the used password through a method called length recovery attack by on-line queries. Second, we crack the known length password using a rainbow table pre-computed with a fixed challenge, which can be done efficiently with great probability through off-line computations. This kind of attack can also be implemented successfully even if the underlying hash function MD5 is replaced with SHA-1 or even SHA-512.

SQLIMW: A New Mechanism against SQL-injection

Abstract: SQL-Injection is an attack for Web applications which are based on database system, and it is one of the most serious security threats for Web application. This paper proposes a new middle-ware-based prevention mechanism: SQLIMW. The SQLIMW avoids SQL-Injection attack from the programmer to the server, and use HASH function to replace encryption. Furthermore, it protects username, password and private key of SQLIMW together by XOR operation and HASH. The proposal provides better security and efficiency.

System and method using partial just-in-time complation to resolve memory access pattern problems in hash table probing

Abstract: A system and method for just in time compilation for hash table probing are disclosed. In one implementation, the method of using just-in-time compilation is used to combine the stages of hash value computation and initial lookup into a single compound operation. In another implementation, the method of using just-in-time compilation is used to combine the stages of a hash table record and input record checking to detect if these records are equal, and if not, fetching the next possible record in the linked list of the per-bucket records.

Real time password generation apparatus and method

Abstract: A method and apparatus for generating a password in real time by creating at least one password map during creation of an account associated with a user, and generating and providing a random password hint sequence grid to the user in real time, authenticating the user for accessing the account using a password created by the user, where the password is created by the user using the random password hint sequence grid and the at least one password map.

Cross system secure logon

Abstract: A cross system secure logon in a target system by using a first authentication system and a second authentication system. A correct password may be valid on the first authentication system and the second authentication system. An aspect includes receiving an input password, generating a first hash key by using the first authentication system, and/or generating a second hash key by using the second authentication system, wherein each authentication system uses a system unique non-collision free hash algorithm. Further, in one aspect, comparing the first hash key with a first predefined hash key of the correct password stored in the first authentication system, and/or comparing the second hash key with a second predefined hash key of the correct password stored in the second authentication system. Furthermore, granting access to the target system based on at least one of the comparisons.

Enhanced Dictionary Based Rainbow Table

Abstract: As users become increasingly aware of the need to adopt strong password, it brings challenges to digital forensics investigators due to the password protection of potential evidentiary data. On the other hand, due to human nature and their tendency to select memorable passwords, which compromises security for convenience, users may select strong passwords by considering a permutation of dictionary words. In this paper, we discuss the existing password recovery methods and briefly present our previous work on the design of a time-memory tradeoff pre-computed table (Enhanced Rainbow Table) for efficient random password recovery. We then propose the design of an Enhanced Dictionary Based Rainbow Table to integrate the construction of dictionary based permutated passwords and common passwords within the Enhanced Rainbow Table, to incorporate the two promising password recovery approaches. We then present the analysis of the proposed method.

Stochastic approach on hash cracking

Abstract: Hash functions are used everywhere today, from wireless communications to password storage. Some of them are proven to be mathematically insecure, but still the only way to crack most of them is a brute-force or dictionary attack. Brute-force is usually discarded as an option since it consumes huge amounts of time. Dictionary attack is a regular approach on hash cracking. The attack is performed by selecting words from a dictionary and comparing their hashed value to the obtained value. Word selection is usually done sequentially, which indicates a very long execution time if the searched word is located at the end of the dictionary. This paper introduces a stochastic approach on word selection in a dictionary attack and shows that the approach is desirable if the searched word is found in the second half of the wordlist.

A Lock-Free Concurrent Hash Table Design for Effective Information Storage and Retrieval on Large Data Sets.

Abstract: The purpose of this work is to develop a lock-free hash table that allows a large number of threads to concurrently insert, modify, or retrieve information. Lock-free or nonblocking designs alleviate the problems traditionally associated with lock-based designs, such as bottlenecks and thread safety. Using standard atomic operations provided by the hardware, the design is portable and therefore, applicable to embedded systems and supercomputers such as the Cray XMT. Real-world applications range from search-indexing to computer vision. Having written and tested the core functionality of the hash table, we plan to perform a formal validation using model checkers.

A new variant of time memory trade-off on the improvement of thing and ying's attack

Abstract: In this paper, we present a rigorous evaluation of Thing and Ying's attack (TY attack) [11] along with practical implementations. We find that the cryptanalysis time of their attack is too high to be practical. We also propose a more general time memory trade-off by combining the distinguished points strategy with TY attack. Both theoretical analysis and experimental results show that our new design can save about 53.7% cryptanalysis time compared to TY attack and can reduce about 35.2% storage requirement compared to the original rainbow attack.

Password Authentication Scheme with Secured Login Interface

Abstract: This paper presents a novel solution to the age long problem of password security at input level. In our solution, each of the various characters from which a password could be composed is encoded with a random single digit integer and presented to the user via an input interface form. A legitimate user entering his password only needs to carefully study the sequence of code that describe his password, and then enter these code in place of his actual password characters. This approach does not require the input code to be hidden from anyone or converted to placeholder characters for security reasons. Our solution engine regenerates new code for each character each time the carriage return key is struck, producing a hardened password that is convincingly more secure than conventional password entry system against both online and offline attackers. Using empirical data and a prototype implementation of our scheme, we give evidence that our approach is viable in practice, in terms of ease of use, improved security, and performance

A One-Time Server-Specific Password Authentication Scheme

Abstract: Over the years, Password-based Authentication (PA) techniques have been the widely used security mechanism that serves as a first level defence against unauthorised access. However, it is paramount that existing PA techniques should be improved upon in order to adequately protect computer systems and networks from password attacks. This work presents a One-Time Server-Specific Password Authentication Scheme (OTSSPAS) for preventing password related attacks. In this work, two protocols known as Password Joggling Protocol (PJP) and Account Management Protocol (AMP) were developed and integrated with OTSSPAS. PJP involves the use of a Password Security Key (PSK) in order to dissuade adversaries from tapping the password. AMP provides an enhanced account management system by considering previous key activities of users in making account locking decision. OTSSPAS adoptsMD5 standard hashing technique for protection of passwords before transmit and storage. Microsoft Visual C# and ASP.Net programming languages were used to implement the design. The evaluation result truly shows that the scheme can prevent common password related attacks.

Development and performance analysis of HPC based framework for cryptanalytic attacks

Abstract: Cryptanalysis is an art of breaking cryptographic algorithms. Cryptanalyzing an algorithm is extremely important to measure its strength. Modern cryptographic algorithms are extremely complex and require huge computing power and resources to break them. A strong algorithm will be infeasible to break given the best technology available but a weak algorithm can be broken easily. Our aim in this research is to develop a framework for attacking cryptographic algorithms using supercomputing infrastructure. This would help us in assessing the strength of an algorithm by measuring the complexities involved. In this paper we present the attack methodology used and the framework developed. Using this framework, we attack DES algorithm and analyze the time and storage complexities. This framework can be in future used for attacking and analyzing the strength of any encryption algorithm.

A General Way to Break Hash-based Challenge-and-Response

Abstract: Hash-based challenge-and-response protocols are widely used as an authentication scheme in network applications. The authenticator sends a random string as a challenge to the peer, the peer generates a response with a hash function on a pre-shared password combined the received challenge. In this paper, we propose a general and efficient way to break some prevalent hash-based challenge- and-response protocols in use. These protocols are vulnerable to the chosen challenge attack launched by a malicious user, who impersonates the server. We first generate a rainbow table containing hash values of all possible passwords, which is produced by hashing a pre-chosen challenge concatenated with all possible password candidates. Second, we impersonate the authenticator and send the pre-chosen challenge to the peer. Finally, we look up in the rainbow table for the received response from the peer to crack the password. With this tactic, we can do the cost consuming pre-computation once, and then we can always use it to recover all of the peer's passwords with only one additional on-line query.

Rainbow Table based on Generator-A New Way of Rainbow Table Generation

Abstract: Rainbow tables are usually used to crack hash passwords,and it could effectively improve the crack speed.However,the time cost for generating a long-password(more than 10 characters) rainbow table could not be tolerated,and the cracking also has a low success rate.A new idea of rainbow table based on generator is proposed,and this rainbow table could greatly compress the plaintext space.It is based on some universal law of the process of artificial long passwords,and in this way a lot of low-probability passwords are removed from the plaintext space.It makes the generation of rainbow table for long passwords acceptable and provides an operable method to crack artificial long passwords.

Hash table using hash table banks

Abstract: A hash table method and structure comprises a processor that receives a plurality of access requests for access to a storage device. The processor performs a plurality of hash processes on the access requests to generate a first number of addresses for each access request. Such addresses are within a full address range. Hash table banks are operatively connected to the processor. The hash table banks form the storage device. Each of the hash table banks has a plurality of input ports. Specifically, each of the hash table banks has less input ports than the first number of addresses for each access request. The processor provides the addresses to the hash table banks, and each of the hash table banks stores pointers corresponding to a different limited range of addresses within the full address range (each of the different limited range of addresses is less than the full address range).

Prover and Verifier Based Password Protection: PVBPP

Abstract: In today's world password are mostly used for authentication. This makes them prone to various kinds of attacks like dictionary attacks. A dictionary attack is a method of breaking the password by systematically entering every word in a dictionary as a password. This attack leads to an overload on the server leading to denial of service attack. This paper presents a protocol to reduce the rate of dictionary attack by using a prover and a verifier system. This system makes it difficult for the attacker to prove it as a valid user by becoming computationally intensive. The rate of attempts is also reduced and thus restricting the Denial of Service attack.

Hash table storage and search methods and devices

Abstract: A hash table storage method includes: obtaining attribute information of at least two levels of hash tables; sequentially obtaining Key information from a received packet according to the attribute information of the at least two levels of hash tables; sequentially determining whether the Key information is stored in its corresponding hash table; and storing the Key information in its corresponding hash table if the Key information is not stored in its corresponding hash table.

Password Cracking Based On Rainbow Tables With A Dynamically Coarse Grain Reconfigurable Architecture

Abstract: Rainbow attack is a very efficient attack which uses rainbow tables to offer an almost optimal time-memory tradeoff in the process of recovering the plaintext password from ciphertext hash. In this paper, we proposed a new method which can crack DES password quickly with less power consumption on a coarse grain reconfigurable architecture (CGRA) named reconfigurable encrypt-decrypt system (REEDS). To the best of our knowledge, this is the first try for password cracking based on “Rainbow Tables” under a dynamically CGRA platform presented in the literature. High parallel computing capability and good flexibility make the platform an excellent candidate to process multimedia application, encryption and decryption algorithm etc. In this paper, the whole work of DES password cracking based on rainbow tables is split into several sub tasks, which are mapped onto REEDS respectively and executed in parallel using pipeline approach. Experimental results show that the proposed system with 200 MHz clock r...