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Eli Biham - One of the best experts on this subject based on the ideXlab platform.

  • Cryptanalysis of Triple Modes of Operation
    Journal of Cryptology, 1999
    Co-Authors: Eli Biham
    Abstract:

    Multiple Modes of Operation and, in particular, triple Modes of Operation were proposed as a simple method to improve the strength of blockciphers, and in particular of DES. Developments in the cryptanalysis of DES in recent years have popularized the triple Modes of DES, and such Modes are now considered for ANSI standards. In a previous paper we analyzed multiple Modes of Operation and showed that the security of many multiple Modes is significantly smaller than expected. In this paper we extend these results, with new cryptanalytic techniques, and show that all the (cascaded) triple Modes of Operation are not much more secure than a single encryption--in the case of DES they can be attacked with up to an order of 2 56 --2 66 chosen plaintexts or ciphertexts and complexity of analysis. We then propose several candidates for more secure Modes.

  • Cryptanalysis of Multiple Modes of Operation
    Journal of Cryptology, 1998
    Co-Authors: Eli Biham
    Abstract:

    In recent years, several new attacks on DES were introduced. These attacks have led researchers to suggest stronger replacements for DES, and in particular new Modes of Operation for DES. The most popular new Modes are triple DES variants, which are claimed to be as secure as triple DES. To speed up hardware implementations of these Modes, and to increase the avalanche, many suggestions apply several standard Modes sequentially. In this paper we study these multiple (cascade) Modes of Operation. This study shows that many multiple Modes are much weaker than multiple DES, and their strength is theoretically comparable to a single DES. We conjecture that Operation Modes should be designed around an underlying cryptosystem without any attempt to use intermediate data as feedback, or to mix the feedback into an intermediate round. Thus, in particular, triple DES used in CBC mode is more secure than three single DESs used in triple CBC mode. Alternatively, if several encryptions are applied to each block, the best choice is to concatenate them to one long encryption, and build the mode of Operation around it.

  • ASIACRYPT - Cryptanalysis of Multiple Modes of Operation
    Advances in Cryptology — ASIACRYPT'94, 1995
    Co-Authors: Eli Biham
    Abstract:

    In recent years, several new attacks on DES were introduced. These attacks have led researchers to suggest stronger replacements for DES, and in particular new Modes of Operation for DES. The most popular new Modes are triple DES variants, which are claimed to be as secure as triple DES. To speed up hardware implementations of these Modes, and to increase the avalanche, many suggestions apply several standard Modes sequentially. In this paper we study these multiple (cascade) Modes of Operation. This study shows that many multiple Modes are much weaker than multiple DES, and their strength is comparable to a single DES.

  • FSE - On Modes of Operation
    Fast Software Encryption, 1994
    Co-Authors: Eli Biham
    Abstract:

    In this paper we study the Modes of Operation in which a cryptosystem, and in particular DES, can be used. This study shows that attempts to complicate the Modes of Operation weaken (in many cases) the resultant Modes. We conclude that Operation Modes should be designed around the underlying cryptosystem without any attempt to use intermediate data as feedback, or to mix the feedback into an intermediate round. Thus, in particular, triple-DES used in CBC mode is more secure than a single-DES used in triple-CBC mode. Alternatively, if several encryptions are applied to each block, the best choice is to concatenate them to one long encryption, and build the mode of Operation around it.

Josep M Guerrero - One of the best experts on this subject based on the ideXlab platform.

  • single phase microgrid with seamless transition capabilities between Modes of Operation
    IEEE Transactions on Smart Grid, 2015
    Co-Authors: Alexander Micallef, M Apap, Cyril Spiteristaines, Josep M Guerrero
    Abstract:

    Microgrids are an effective way to increase the penetration of distributed generation into the grid. They are capable of operating either in grid-connected or in islanded mode, thereby increasing the supply reliability for the end user. This paper focuses on achieving seamless transitions from islanded to grid-connected and vice versa for a single phase microgrid made up from voltage controlled voltage source inverters (VC-VSIs) and current controlled voltage source inverters (CC-VSIs) working together in both Modes of Operation. The primary control structures for the VC-VSIs and CC-VSIs is considered together with the secondary control loops that are used to synchronize the microgrid as a single unit to the grid. Simulation results are given that show the seamless transitions between the two Modes without any disconnection times for the CC-VSIs and VC-VSIs connected to the microgrid.

Bihameli - One of the best experts on this subject based on the ideXlab platform.

Giri Venkataramanan - One of the best experts on this subject based on the ideXlab platform.

  • current source rectifiers in discontinuous conduction Modes of Operation
    IEEE Transactions on Industry Applications, 2015
    Co-Authors: Robert Cuzner, Giri Venkataramanan
    Abstract:

    Although the Operation of a three-phase current source rectifier (CSR) for ac-to-dc conversion using phase control or low-frequency pulse control is well established in a wide variety of applications, CSR realization using high-frequency pulsewidth-modulation control has been recently studied as a potentially competitive alternative to a voltage source rectifier. In the CSR, reverse blocking gate turn-off switches are realized using series-connected diodes, which prevent any reversal of the dc-link current. A significant consequence of this limitation occurs at light load conditions. The dc-link inductor current enters the discontinuous mode of Operation and leads to the loss of the control of the output voltage and a highly distorted input current, which compromise the potential advantages of the approach. This paper characterizes the CSR while operating in the discontinuous conduction mode and proposes a modulation strategy that restores the control of the output voltage and ensures a nearly sinusoidal current at light loads. Simulation and hardware results are provided for a 3-kW laboratory-scale prototype system.

  • current source rectifiers in discontinuous conduction Modes of Operation
    Energy Conversion Congress and Exposition, 2013
    Co-Authors: Robert Cuzner, Giri Venkataramanan
    Abstract:

    While Operation of the three phase Current Source Rectifier (CSR) for ac-to-dc conversion using phase control or low frequency pulse control is well established in a wide variety of applications, CSR realization using high frequency Pulse-Width-Modulation (PWM) control is being studied recently as a potentially competitive alternative to a Voltage Source Rectifier (VSR). In the CSR reverse blocking gate turn-off switches are realized using series connected diodes, which prevent any reversal of the dc link current. A significant consequence of this limitation occurs at light load conditions. The dc link inductor current enters discontinuous mode of Operation and leads to loss of control of output voltage and highly distorted input current, which compromises the potential advantages of the approach. This paper characterizes the CSR while operating in discontinuous conduction mode and proposes a modulation strategy which restores control of output voltage and ensures nearly sinusoidal current at light loads. Simulation and hardware results are provided for a 3kW laboratory scale prototype system.

Alexander Micallef - One of the best experts on this subject based on the ideXlab platform.

  • single phase microgrid with seamless transition capabilities between Modes of Operation
    IEEE Transactions on Smart Grid, 2015
    Co-Authors: Alexander Micallef, M Apap, Cyril Spiteristaines, Josep M Guerrero
    Abstract:

    Microgrids are an effective way to increase the penetration of distributed generation into the grid. They are capable of operating either in grid-connected or in islanded mode, thereby increasing the supply reliability for the end user. This paper focuses on achieving seamless transitions from islanded to grid-connected and vice versa for a single phase microgrid made up from voltage controlled voltage source inverters (VC-VSIs) and current controlled voltage source inverters (CC-VSIs) working together in both Modes of Operation. The primary control structures for the VC-VSIs and CC-VSIs is considered together with the secondary control loops that are used to synchronize the microgrid as a single unit to the grid. Simulation results are given that show the seamless transitions between the two Modes without any disconnection times for the CC-VSIs and VC-VSIs connected to the microgrid.