The Crime
The Crime
As mentioned in the home page, cryptanalysis is essentially codebreaking. It can be done legally. For example, a system�s designer may want to evaluate if that system is secure. But hostile attackers might undertake the task, hoping to corrupt a system or gain classified knowledge. This is where it gets ugly.
Can every code be broken? Most people wrongly believe that the answer is yes. Claude Shannon, however, proved that to be false. He proved that the one-time pad cipher in unbreakable. He provided that the key material is most definitely random is never reused. It is kept secret from all possible attackers and it is of equal or greater length than the original message. Aside from this cipher, most encryption can be broken, as long as there is enough computational effort. This amount of effort needed to break a code may be astronomically high compared to the amount of effort it takes to actually use it. In cases such as these, security can still be reached if the guidelines are big enough that the effort it would take to crack the code is beyond the ability of the attacker.
There is a wide variety of attacks that can be classified in many different ways. One way to classify these attacks depends on what an attacker knows and does in order to crack the code.
| Cryptanalytic Attacks | Implementation Attacks | |||||
| Ciphertext Only | Known-Plaintext | Chosen Plaintext | Chosen Ciphertext | Side-Channel | Traffic Analysis | |
| The attacker has access to... | only the ciphertext. | the ciphertext and the corresponding plaintext. | his choice of plaintext. | his choice of ciphertext. | the amount of time it took for the algorithm to encrypt the message. | the pattern of the cipher and the length of the message. |
| Other Important Information | Modern cryptosystems are usually immune to this type of attack. | The attacker may have access to many pairs like these. | The attacker learns the corresponding ciphertext, and he often learns it multiple times. | The attacker learns the corresponding plaintext. | The attacker can use a timing attack to break a cipher that is resistant to analysis. | The attacker studies this information to find valuable, secret information. |
Ever since computers became �mainstream�, there has been controversy that has been surrounding cryptography. The export of cryptography and related items has been an important issue. Cryptanalysis was used heavily in World War II, resulting in the strict regulation of the export of cryptography due to national security concerns. This was not a problem until the Internet became popular. With the growth of the Internet, most standard encryption techniques became globally well known. The restrictions on exports were a major obstacle in research. As a result of several challenges against these regulations on exporting cryptography, exports from the United States are not regulated as strictly as they were in the past. However, encryption that surpasses the allowed strengths is still considered a crime against the United States.
Cryptography also plays a major part in digital rights management, which is a technological way of enforcing copyrights. President Clinton signed the Digital Millenium Copyright Act in 1998, criminalizing the production and publication of some cryptanalytic techniques and technology. A case could be made that basically any cryptanalytic research violates the DMCA. However, the DMCA has not been enforced as strictly feared. Regardless, the act is still a hot topic in they cryptography community.
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Click here to learn more about the main types of
encryption.
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