Battery Power
Chandramouli, R., Bapatla, S., & Subbalakshmi, K.P. (2006). Battery Power-Aware Encryption. ACM Transactions on Information Security and System Security, 9, 162-180. Retrieved on September 13, 2006, from the ACM Digital Library database.
Because the battery power of wireless devices is limited, they are vulnerable to attacks such as brute-force cryptanalysis attacks when their security parameters cannot be supported due to low battery power. The authors’ goal is to model and measure power usage of crypto algorithms to identify and thus minimize such security risks.
The stream and block ciphers the authors used for this paper were DES (a 64 bit symmetric block cipher), IDEA (a 64-bit plaintext block cipher), GOST (a 64-bit block encryption algorithm), and RC4 (a variable key-size cipher with a key stream independent of the plaintext). For the experimental hardware portion used to gather power consumption data, the writers used a laptop running a version of Oprofile for Red Hat Linux 2.4.8 adapted to monitor power value for different functions. The power used by the laptop to encrypt and decrypt algorithms in ten random plaintext data sets was measured as a function of the power going into the laptop, and the power consumption value was calculated as the product of the current and voltage used. The profiled data obtained from running the encryption algorithms on the laptop showed that power consumption changed linearly with the number of rounds in the DES, IDEA, and GOST encryption algorithms. (When the two part algorithm of substitution and permutation is applied once with a key, this is termed a “round”). The rate of change of power with respect to the number of rounds was the largest for IDEA, the smallest for GOST, and the power consumption of RC4 varied non-linearly with respect to the length of the key.
Although often used, the authors observed that there are no constructions of block ciphers that offer unconditional security. In order to assess the effectiveness of an encryption algorithm, they proposed subjecting it to a cryptanalysis attack such as a brute-force attack in which all possible encryption keys are tested. Since rounds and key length affect power consumed, a measure of security can be determined by comparing block cipher vulnerability in such an attack. By considering a linear attack of the DES algorithm, the authors determined that the vulnerability of a cipher can be defined as a ratio of the maximum number of block length plaintexts for such an attack to the number of plaintexts using a cryptanalysis algorithm.
To optimally allocate the battery power for a given number of data packets, each with different security requirements, without exceeding the power available, they proposed optimization formulation 1 and arrived at an algorithm they called GreedyAlloc_Power. Also, to determine optimal battery power where a relationship between plaintext-ciphertext pairs and cryptanalysis success rate is unavailable, the authors proposed optimization formulation 2 and arrived at an algorithm they called GreedyAlloc_Round. When the authors used the GreedyAlloc_Power algorithm, they found that an equal allocation of power to all packets regardless of vulnerability was inefficient, and when using GreedyAlloc_Round, that the cryptanalyst needed a factor of 2^8 more plaintexts to equal the performance of equal resource allocation.
In conclusion, the authors theorized that by using the algorithms they proposed, security provided by encryption algorithms can be optimized within the power limitations of a battery-powered device.
Because the battery power of wireless devices is limited, they are vulnerable to attacks such as brute-force cryptanalysis attacks when their security parameters cannot be supported due to low battery power. The authors’ goal is to model and measure power usage of crypto algorithms to identify and thus minimize such security risks.
The stream and block ciphers the authors used for this paper were DES (a 64 bit symmetric block cipher), IDEA (a 64-bit plaintext block cipher), GOST (a 64-bit block encryption algorithm), and RC4 (a variable key-size cipher with a key stream independent of the plaintext). For the experimental hardware portion used to gather power consumption data, the writers used a laptop running a version of Oprofile for Red Hat Linux 2.4.8 adapted to monitor power value for different functions. The power used by the laptop to encrypt and decrypt algorithms in ten random plaintext data sets was measured as a function of the power going into the laptop, and the power consumption value was calculated as the product of the current and voltage used. The profiled data obtained from running the encryption algorithms on the laptop showed that power consumption changed linearly with the number of rounds in the DES, IDEA, and GOST encryption algorithms. (When the two part algorithm of substitution and permutation is applied once with a key, this is termed a “round”). The rate of change of power with respect to the number of rounds was the largest for IDEA, the smallest for GOST, and the power consumption of RC4 varied non-linearly with respect to the length of the key.
Although often used, the authors observed that there are no constructions of block ciphers that offer unconditional security. In order to assess the effectiveness of an encryption algorithm, they proposed subjecting it to a cryptanalysis attack such as a brute-force attack in which all possible encryption keys are tested. Since rounds and key length affect power consumed, a measure of security can be determined by comparing block cipher vulnerability in such an attack. By considering a linear attack of the DES algorithm, the authors determined that the vulnerability of a cipher can be defined as a ratio of the maximum number of block length plaintexts for such an attack to the number of plaintexts using a cryptanalysis algorithm.
To optimally allocate the battery power for a given number of data packets, each with different security requirements, without exceeding the power available, they proposed optimization formulation 1 and arrived at an algorithm they called GreedyAlloc_Power. Also, to determine optimal battery power where a relationship between plaintext-ciphertext pairs and cryptanalysis success rate is unavailable, the authors proposed optimization formulation 2 and arrived at an algorithm they called GreedyAlloc_Round. When the authors used the GreedyAlloc_Power algorithm, they found that an equal allocation of power to all packets regardless of vulnerability was inefficient, and when using GreedyAlloc_Round, that the cryptanalyst needed a factor of 2^8 more plaintexts to equal the performance of equal resource allocation.
In conclusion, the authors theorized that by using the algorithms they proposed, security provided by encryption algorithms can be optimized within the power limitations of a battery-powered device.
posted by Dr. Adam Norten at 4:59 PM
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