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Topic: Ciphertext-only attack

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Ciphertext-only attack - Wikipedia, the free encyclopedia In cryptography, a ciphertext-only attack is a scenario for cryptanalysis where the attacker is assumed to have access only to a set of ciphertexts. Mechanical encryption devices such as Enigma made these attacks much more difficult (although, historically, Polish cryptographers were able to mount a successful ciphertext-only cryptanalysis of the Enigma by exploiting an insecure protocol for indicating the message settings). Nonetheless poor cipher usage or reliance on home-grown proprietary algorithms that have not been subject to thorough scrutiny has resulted in many computer-age encryption systems that are still subject to ciphertext-only attack. en.wikipedia.org /wiki/Ciphertext-only_attack   (461 words)

Adaptive chosen ciphertext attack - Wikipedia, the free encyclopedia An adaptive chosen ciphertext attack is an interactive form of chosen ciphertext attack in which an attacker sends a number of ciphertexts to be decrypted, then uses the results of these decryptions to select subsequent ciphertexts. For public-key systems, adaptive chosen ciphertexts are generally applicable only when they have the property of ciphertext malleability — that is, a ciphertext can be modified in specific ways that will have a predictable effect on the decryption of that message. In order to prevent adaptive chosen ciphertext attacks, it is necessary to use an encryption or encoding scheme that limits ciphertext malleability. www.wikipedia.org /wiki/Adaptive_chosen_ciphertext_attack   (290 words)

Madryga A ciphertext-only attack is devastating for a modern block cipher; as such, it is probably more prudent to use another algorithm for encrypting sensitive data. Biryukov and Kushilevitz (1998) published an improved differential attack requiring only 16 chosen-plaintext pairs, and then demonstrated that it could be converted to a ciphertext-only attack using 2 He noticed that "the parity of all the bits of the plaintext and the ciphertext is a constant, depending only on the key. www.serebella.com /encyclopedia/article-Madryga.html   (719 words)

Man in the middle attack - Wikipedia, the free encyclopedia While this example focuses on the MITM attack in a cryptographic context, MITM should be seen as a general problem resulting from any use of intermediate parties acting as a proxy for the clients on either side. The MITM attack is particularly applicable to the original Diffie-Hellman key exchange protocol, when used without authentication. In cryptography, a man in the middle attack (MITM) is an attack in which an attacker is able to read, insert and modify at will, messages between two parties without either party knowing that the link between them has been compromised. en.wikipedia.org /wiki/Man_in_the_middle_attack   (678 words)

Global System for Mobile Communications - Wikipedia, the free encyclopedia Serious weaknesses have been found in both algorithms, and it is possible to break A5/2 in real-time in a ciphertext-only attack. Originally it was intended only to produce the specifications of the next (third, 3G) generation of mobile networks. Some operators will block this by allowing the phone to use only a single SIM, or only a SIM issued by them; this practice is known as SIM locking, and is illegal in some countries. en.wikipedia.org /wiki/GSM   (1805 words)

Rob Slade's Security Glossary Attack is often used as a synonym for a specific exploit. An attack may be active, resulting in the alteration of data; or passive, resulting in the release of data. This form of malicious attack is particularly suited to viruses where no data is actually erased or corrupted but where system resources are occupied to the extent that normal service is restricted. www.philosophy.niu.edu /~rslade/secgloss.htm   (14720 words)

R2comments.txt For the example, the only possible inputs for the Rijndael S-box are 225 and 135 225 ^ 135 = 102 S(225) ^ S(135) = 248 ^ 23 = 239 Now the attacker knows that the W1[3][1] must be a 225 or a 135. This only adds a small amount of latency when compared to an unpipelined single round (limited solely to partitioning effects and the setup and hold time of the flip-flops) a small amount of area (the pipeline registers, which may be free depending on the implementation technology), while greatly improving bandwidth. The only thing that we can ask is not "Is AES secure enough?" but "How many round of AES is secure enough for now?" The only problem is changing also the algorithm of key scheduling, so the specification of key scheduling which makes it possible to increase the number of rounds should be given. csrc.nist.gov /encryption/aes/round2/comments/R2comments.txt   (19029 words)

Re: [GSMSecurity] GSM security flaw uncovered We describe a ciphertext-only attack on A5/2 that requires a few dozen milliseconds of encrypted off-the-air cellular conversation and finds the correct key in less than a second on a personal computer. For those who have not read the paper, you may be interested in taking a look at the copy which has been uploaded to Cryptome: http://cryptome.org/gsm-crack-bbk.pdf (18 Pages, 233KB) "Instant Ciphertext-Only Cryptanalysis of GSM Encrypted Communications" by Elad Barkan, Eli Biham, Nathan Keller. We emphasize that these attacks are on the protocols, and are thus applicable whenever the cellular phone supports a weak cipher, for instance they are also applicable using the cryptanalysis of A5/1. lists.virus.org /gsmsecurity-0309/msg00021.html   (344 words)

CIPHERTEXT-ONLY CRYPTANALYSIS OF ENIGMA If this attack was beyond the technology of Bletchley Park during the war, it was certainly accessible only a few years later. The attack exploits a weakness in the use of the plugboard: not all letters are interchanged. This attack appears to be practical for the level of traffic decrypted at Bletchley Park for keys using up to nine or ten plugs. www.fortunecity.com /skyscraper/coding/379/gillog1.htm   (2196 words)

IP Workshop - Tygar/Yee: Dyad A chosen-ciphertext attack is one where the attacker may chose some ciphertext messages and obtain their corresponding plaintext in an attempt to derive the key used. A chosen-plaintext attack is one where the attacker may chose plaintext messages and obtain the corresponding ciphertext in an attempt to decrypt other messages or derive the key. Another physical attack is the use of solvents to dissolve the potting material to expose the sensor wires. www.cni.org /docs/ima.ip-workshop/Tygar.Yee.html   (13018 words)

cryptfaq.txt A cyphertext only attack is usually presumed to be possible, and a code's resistance to it is considered the basis of its cryptographic security. To summarize, the basic types of cryptanalytic attacks in order of difficulty for the attacker, hardest first, are: cyphertext only: the attacker has only the encoded message from which to determine the plaintext, with no knowledge whatsoever of the latter. Unicity distance, like all statistical or information-theoretic measures, does not make deterministic predictions but rather gives probabilistic results: namely, the minimum amount of ciphertext for which it is likely that there is only a single intelligible plaintext corresponding to the ciphertext, when all possible keys are tried for the decryption. www.hackcanada.com /blackcrawl/encrypt/cryptfaq.txt   (13766 words)

Timing attack -- Facts, Info, and Encyclopedia article The attack exploits the fact that in an (Click link for more info and facts about asymmetric key algorithm) asymmetric key algorithm, computation time for a private key operation is dependent on the key in some way. The attack requires that the adversary know the internals of the implementation. Timing attack -- Facts, Info, and Encyclopedia article www.absoluteastronomy.com /encyclopedia/T/Ti/Timing_attack.htm   (285 words)

IBM Research Research Areas Security The contribution of this paper is to present two very practical threshold cryptosystems, and to prove that they are secure against chosen ciphertext attack in the random oracle model. For the most compelling applications of threshold cryptosystems, security against chosen ciphertext attack is a requirement. However, prior to the results presented here, there appeared to be no practical threshold cryptosystems in the literature that were provably chosen-ciphertext Securing Threshold Cryptosystems against Chosen Ciphertext Attack (p3 of 233) secure, even in the idealized random oracle model. www.research.ibm.com /compsci/spotlight/security/papers.html   (726 words)

11th Annual USENIX Security Symposium — Technical Paper Mirroring the side-channel attacks of Bleichenbacher [Ble98] and Manger [Man01] on asymmetric schemes, he showed that symmetric encryption methods are just as vulnerable to side-channel weaknesses when an adversary is able to distinguish between valid and invalid ciphertexts. However, each attack we examined depended on the adversary's ability to freely and predictably alter bits of the plaintext via manipulation of the ciphertext, and this ability was granted by each of the symmetric encryption schemes considered. Also in [Bel96], an attack (very similar to the attacks in this paper) is described which recovers plaintext bits by sending altered ciphertexts to a TCP peer which then acts as a validity oracle for each packet by either dropping it or returning an ACK for it. www.usenix.org /event/sec02/full_papers/black/black_html   (6117 words)

Q63: At What Point Does an Attack Become Practical? Note that some knowledge of the statistical distribution of the plaintext is required for a ciphertext-only attack to succeed. One classification distinguishes among cryptanalytic attacks according to the data they require in the following way: chosen plaintext or chosen ciphertext, known plaintext, and ciphertext-only. A known plaintext attack is more useful to the cryptanalyst than a chosen plaintext attack (with the same amount of data) since the cryptanalyst now requires a certain numbers of plaintexts and their corresponding ciphertexts without specifying the values of the plaintexts. www.notworking.com /faqs/crypto/q63.html   (361 words)

Chosen Ciphertext Attack against SILC private messages Problem of this attack is that it cannot be done without compromised SILC server, and it may work only once or twice because Bob will get suspicious easily of receiving corrupted messages and starts to investigate the matter. I haven't tried this attack in practice, only on paper. The attack requires compromised SILC server, and it requires social engineering from the adversary to delude the victim to think that he is the original message sender. phuture.sk /pipermail/silc-users/2002-October/000087.html   (903 words)

Rob Slade's Security Glossary Attack is often used as a synonym for a specific exploit. An attack may be active, resulting in the alteration of data; or passive, resulting in the release of data. This form of malicious attack is particularly suited to viruses where no data is actually erased or corrupted but where system resources are occupied to the extent that normal service is restricted. www.philosophy.niu.edu /~rslade/secgloss.htm   (14720 words)

Zvon - RFC 2437 [PKCS #1: RSA Cryptography Specifications Version 2.0] - Encryption schemes It is possible that in a protocol on which both encryption schemes are present, an adaptive chosen ciphertext attack such as [4] would be useful. Another flavor of the attack is successful in decrypting a single ciphertext when a large fraction (2/3) of the input to RSAEP is already known. An encryption scheme consists of an encryption operation and a decryption operation, where the encryption operation produces a ciphertext from a message with a recipient's public key, and the decryption operation recovers the message from the ciphertext with the recipient's corresponding private key. www.zvon.org /tmRFC/RFC2437/Output/chapter7.html   (1773 words)

RFC 3218 - (rfc3218) - Preventing the Million Message Attack on Cryptographic Message Syntax The attacker first captures the ciphertext in transit and then uses the recipient as an oracle to recover the plaintext by sending transformed versions of the ciphertext and observing the recipient's response. Call the ciphertext C. The attacker then generates a series of integers S and computes C'=C*(S^e) mod n. This attack, called the Million Message Attack, allowed the recovery of a single PKCS-1 encrypted block, provided that the Rescorla Informational [Page 1] RFC 3218 Preventing the Million Message Attack on CMS January 2002 attacker could convince the receiver to act as a particular kind of oracle. www.rfcsearch.org /rfcview/RFC/3218.html   (1886 words)

Encyclopedia: Passive attack This can also include known plaintext attacks where both the plaintext and its corresponding ciphertext are known. See also: Chosen plaintext attack, Chosen ciphertext attack, Adaptive chosen ciphertext attack, topics in cryptography. A passive attack on a cryptosystem is one in which the cryptanalyst cannot interact with any of the parties involved, attempting to break the system solely based upon observed data (i.e. www.nationmaster.com /encyclopedia/Passive-attack   (142 words)

CRYPTO '98: 18th Annual Cryptology Conference The attack requires on the order of a million trials, however, and is therefore only applicable to cases with the recipient implementation automatically responds to an error (i.e. Encryption with proof of plaintext knowledge prevents captured ciphertext attacks, such as Bleichenbacher's attack on the SSL protocol using PKCS #1. Their attack does not work on SHA-1, the revised version of SHA, suggesting that the unexplained change in the US standard hash function was a correction of this weakness. www.ieee-security.org /Cipher/ConfReports/conf-rep-crypto98.html   (3137 words)

key-as-iv-broken-again Under the premises of the chosen-ciphertext attack, the attacker obtains the decryption of the modified ciphertext. In an active attack, suppose you intercept a new ciphertext C'[0],C'[1],... This attack requires one chosen-ciphertext query, a little bit of known plaintext, and very little computation. www.cs.berkeley.edu /~daw/my-posts/key-as-iv-broken-again   (404 words)

nCipher Security Glossary A cryptanalyst can mount an attack of this type in a scenario in which he or she has free use of a piece of decryption hardware, but is unable to extract the decryption key from it. A special case of the chosen-plaintext attack in which the cryptanalyst is able to choose plaintexts dynamically, and alter his or her choices based on the results of previous encryptions. The ciphertext may be read by anyone who has the key that decrypts (undoes the encryption of) the ciphertext. www.ncipher.com /investors/glossary.php   (4708 words)

Anand Desai: publications The goal is to have secure encryption modes with the additional property that exhaustive key-search attacks on them are slowed down by a factor equal to the number of blocks in the ciphertext. Unlike block ciphers, that can work with only one fixed length (the block length), a variable-input-length cipher can work with inputs of arbitrary and varying lengths. It asks that an eavesdropper in possession of a ciphertext not be able to tell which specific key, out of a set of known public keys, is the one under which the ciphertext was created, meaning the receiver is anonymous from the point of view of the adversary. www-cse.ucsd.edu /users/adesai/papers/pubs.html   (1261 words)

RSA Analysis of PKCS 1 Attack Were the encoding method plaintext-aware, of course, the probability that a ciphertext is “good” would be negligible, thereby defeating the attack. A ciphertext is “good” if the recipient does not output an error message indicating that the format of corresponding plaintext does not conform with PKCS #1. A large number may indicate that an attack is in progress, and that the recipient should determine their source. cryptome.sabotage.org /rsa-pkcs1.htm   (2253 words)

Content.html adaptive chosen plaintext and chosen cipherte xt attack Click here to get our Style Agreements (in Word format) www.win.tue.nl /~henkvt/Content.html   (2253 words)

ciphertext-only attacks From what I understand, to prove formally that a cryptosystem is secure against ciphertext-only attacks, we would have to show a reduction from algorithm A beating the system into algorithm B breaking some well-known assumption, such as DDH or factoring is hard. But I guess the latter is a moot question, since ciphertext-only security is pretty uninteresting; if you don't have security against known-plaintext attacks, the system is pretty worthless. Alex wrote: =(2) Does anyone know of a paper, which gives a formal proof of =ciphertext-only attack security for a similar scheme --= possibly by =reducing adversary to algorithm for factoring integers. www.totalblowhole.com /new-6316699-4287.html   (961 words)

Cryptology ePrint Archive Moreover it works in much less restrictive conditions that the previous attack, for example knowing ONLY that the ciphertext is in English. For example, the new attack breaks the stream cipher Toyocrypt submitted to the Japanese government Cryptrec call for cryptographic primitives, and one of only two candidates accepted to the second phase of Cryptrec evaluation process. Our new attack allows to break efficiently stream ciphers that are known to be immune to all the previously known attacks. eprint.iacr.org /2002/087   (341 words)

Firewalls Complete - Cryptography: Is it Enough? Only the marked attribute or set of attributes is used in a CS query, this marked set is the common element in distinguished names of certificates located at the server with the correct key, but not all certificates at this location have this common element This version not only checks the passwords against its basic dictionary, but also checks for passwords that are identical to the username, which I used as an example for a cracked password on figure 3.18. The only inconvenient is to know the recipients’ public key, and as its usage increases, there are a lot of public keys out there, without a central place to be stored. www.secinf.net /firewalls_and_VPN/Firewalls_Complete/Firewalls_Complete__Cryptography_Is_it_Enough.html   (15149 words)

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