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A Method for Obtaining Digital Signatures and PublicKey Cryptosystems
 Communications of the ACM
, 1978
"... An encryption method is presented with the novel property that publicly revealing an encryption key does not thereby reveal the corresponding decryption key. This has two important consequences: 1. Couriers or other secure means are not needed to transmit keys, since a message can be enciphered usin ..."
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Cited by 2895 (30 self)
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An encryption method is presented with the novel property that publicly revealing an encryption key does not thereby reveal the corresponding decryption key. This has two important consequences: 1. Couriers or other secure means are not needed to transmit keys, since a message can be enciphered using an encryption key publicly revealed by the intended recipient. Only he can decipher the message, since only he knows the corresponding decryption key. 2. A message can be "signed" using a privately held decryption key. Anyone can verify this signature using the corresponding publicly revealed encryption key. Signatures cannot be forged, and a signer cannot later deny the validity of his signature. This has obvious applications in "electronic mail" and "electronic funds transfer" systems. A message is encrypted by representing it as a number M, raising M to a publicly specified power e, and then taking the remainder when the result is divided by the publicly specified product, n, of two lar...
Selecting Cryptographic Key Sizes
 TO APPEAR IN THE JOURNAL OF CRYPTOLOGY, SPRINGERVERLAG
, 2001
"... In this article we offer guidelines for the determination of key sizes for symmetric cryptosystems, RSA, and discrete logarithm based cryptosystems both over finite fields and over groups of elliptic curves over prime fields. Our recommendations are based on a set of explicitly formulated parameter ..."
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Cited by 253 (6 self)
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In this article we offer guidelines for the determination of key sizes for symmetric cryptosystems, RSA, and discrete logarithm based cryptosystems both over finite fields and over groups of elliptic curves over prime fields. Our recommendations are based on a set of explicitly formulated parameter settings, combined with existing data points about the cryptosystems.
How to protect DES against exhaustive key search
 Journal of Cryptology
, 1996
"... Abstract The block cipher DESX is defined by DESX k:k1:k2 (x) = k2 \Phi DES k (k1 \Phi x), where \Phi denotes bitwise exclusiveor. This construction was first suggested by Rivest as a computationallycheap way to protect DES against exhaustive keysearch attacks. This paper proves, in a formal mode ..."
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Cited by 88 (11 self)
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Abstract The block cipher DESX is defined by DESX k:k1:k2 (x) = k2 \Phi DES k (k1 \Phi x), where \Phi denotes bitwise exclusiveor. This construction was first suggested by Rivest as a computationallycheap way to protect DES against exhaustive keysearch attacks. This paper proves, in a formal model, that the DESX construction is sound. We show that, when F is an idealized block cipher, FX
Efficient DES key search
 School of Computer Science, Carleton University
, 1994
"... Abstract. Despite recent improvements in analytic techniques for attacking the Data Encryption Standard (DES), exhaustive key search remains the most practical and efficient attack. Key search is becoming alarmingly practical. We show how to build an exhaustive DES key search machine for $1 million ..."
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Cited by 66 (0 self)
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Abstract. Despite recent improvements in analytic techniques for attacking the Data Encryption Standard (DES), exhaustive key search remains the most practical and efficient attack. Key search is becoming alarmingly practical. We show how to build an exhaustive DES key search machine for $1 million that can find a key in 3.5 hours on average. The design for such a machine is described in detail for the purpose of assessing the resistance of DES to an exhaustive attack. This design is based on mature technology to avoid making guesses about future capabilities. With this approach, DES keys can be found one to two orders of magnitude faster than other recently proposed designs. The basic machine design can be adapted to attack the standard DES modes of operation for a small penalty in running time. The issues of development cost and machine reliability are examined as well. In light of this work, it would be prudent in many applications to use DES in a tripleencryption mode. 1.
Twofish: A 128Bit Block Cipher
 in First Advanced Encryption Standard (AES) Conference
, 1998
"... Twofish is a 128bit block cipher that accepts a variablelength key up to 256 bits. The cipher is a 16round Feistel network with a bijective F function made up of four keydependent 8by8bit Sboxes, a fixed 4by4 maximum distance separable matrix over GF(2 8 ), a pseudoHadamard transform, bit ..."
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Cited by 54 (8 self)
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Twofish is a 128bit block cipher that accepts a variablelength key up to 256 bits. The cipher is a 16round Feistel network with a bijective F function made up of four keydependent 8by8bit Sboxes, a fixed 4by4 maximum distance separable matrix over GF(2 8 ), a pseudoHadamard transform, bitwise rotations, and a carefully designed key schedule. A fully optimized implementation of Twofish encrypts on a Pentium Pro at 17.8 clock cycles per byte, and an 8bit smart card implementation encrypts at 1660 clock cycles per byte. Twofish can be implemented in hardware in 14000 gates. The design of both the round function and the key schedule permits a wide variety of tradeoffs between speed, software size, key setup time, gate count, and memory. We have extensively cryptanalyzed Twofish; our best attack breaks 5 rounds with 2 22.5 chosen plaintexts and 2 51 effort.
On the Security of Multiple Encryption
 COMMUNICATIONS OF THE ACM
, 1981
"... Double encryption has been suggested to strengthen the Federal Data Encryption Standard (DES). A recent proposal suggests that using two 56bit keys but enciphering 3 times (encrypt with a first key, decrypt with a second key, then encrypt with the first key again) increases security over simple do ..."
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Cited by 47 (0 self)
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Double encryption has been suggested to strengthen the Federal Data Encryption Standard (DES). A recent proposal suggests that using two 56bit keys but enciphering 3 times (encrypt with a first key, decrypt with a second key, then encrypt with the first key again) increases security over simple double encryption. This paper shows that although either technique significantly improves security over single encryption, the new technique does not significantly increase security over simple double encryption. Cryptanalysis of the 112bit key requires about 2^56 operations and words of memory, using a chosen plaintext attack. While DES is used as an example, the technique is applicable to any similar cipher.
Fast Software Encryption Functions
, 1998
"... Encryption hardware is not available on most computer systems in use today. Despite this fact, there is no well accepted encryption function designed for software implementation  instead, hardware designs are emulated in software and the resulting performance loss is tolerated. The obvious solutio ..."
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Cited by 36 (0 self)
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Encryption hardware is not available on most computer systems in use today. Despite this fact, there is no well accepted encryption function designed for software implementation  instead, hardware designs are emulated in software and the resulting performance loss is tolerated. The obvious solution is to design an encryption function for implementation in software. Such an encryption function is presented here  on a SUN 4/260 it can encrypt at 4 to 8 megabits per second. The combination of modern processor speeds and a faster algorithm make software encryption feasible in applications which previously would have required hardware. This will effectively reduce the cost and increase the availability of cryptographic protection.
A KnownPlaintext Attack on TwoKey Triple Encryption
, 1990
"... A chosenplaintext attack on twokey triple encryption noted by Merkle and Hellman is extended to a knownplaintext attack. The knownplaintext attack has lower memory requirements than the chosenplaintext attack, but has a greater running time. ..."
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Cited by 32 (2 self)
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A chosenplaintext attack on twokey triple encryption noted by Merkle and Hellman is extended to a knownplaintext attack. The knownplaintext attack has lower memory requirements than the chosenplaintext attack, but has a greater running time.
Probable Plaintext Cryptanalysis of the IP Security Protocols
 PROCEEDINGS OF THE SYMPOSIUM ON NETWORK AND DISTRIBUTED SYSTEM SECURITY
, 1997
"... The Internet Engineering Task Force (IETF) is in the process of adopting standards for IPlayer encryption and authentication (IPSEC). We describe how "probable plaintext" can be used to aid in cryptanalytic attacks, and analyze the protocol to show how much probable plaintext is available. We also ..."
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Cited by 27 (2 self)
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The Internet Engineering Task Force (IETF) is in the process of adopting standards for IPlayer encryption and authentication (IPSEC). We describe how "probable plaintext" can be used to aid in cryptanalytic attacks, and analyze the protocol to show how much probable plaintext is available. We also show how traffic analysis is a powerful aid to the cryptanalyst. We conclude by outlining some likely changes to the underlying protocols that may strengthen them against these attacks.
Fast DES Implementations for FPGAs and its Application to a Universal KeySearch Machine
 Queen's University
"... . Most modern security protocols and security applications are defined to be algorithm independent, that is, they allow a choice from a set of cryptographic algorithms for the same function. Therefore a keysearch machine which is also defined to be algorithm independent might be interesting. We res ..."
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Cited by 26 (5 self)
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. Most modern security protocols and security applications are defined to be algorithm independent, that is, they allow a choice from a set of cryptographic algorithms for the same function. Therefore a keysearch machine which is also defined to be algorithm independent might be interesting. We researched the feasibility of a universal keysearch machine using the Data Encryption Standard (DES) as an example algorithm. Field Programmable Gate Arrays (FPGA) provide an ideal match for an algorithm independent cracker as they can switch algorithms onthefly and run much faster than software. We designed, implemented and compared various architecture options of DES with strong emphasis on highspeed performance. Techniques like pipelining and loop unrolling were used and their effectiveness for DES on FPGAs investigated. The most interesting result is that we could achieve data rates of up to 403 Mbit/s using a standard Xilinx FPGA. This result is by a factor 31 faster than software imp...