CompTIA Security_ Deluxe Study Guide_ SY0-201 - Emmett Dulaney [172]
Figure 7.3 demonstrates this concept. In this example, each photon is polarized in one of several directions. The process of intercepting these photons alters the polarity of some of the photons and makes the message unreadable. This alerts the receiver that an interception activity is occurring. As you can see in this example, the message has been altered as a result of the interception. Each bar in the message is part of the message: The interception changes the polarity of some of the photons (represented by the bars), making the message unreadable.
Quantum cryptography has become a solution available for private users, although it’s very expensive and has a limited range. It will be interesting to see what the future holds for this technology.
Quantum cryptography is currently only implemented using fiber-optic technology. This technology, when further developed, may make many of the systems now in use obsolete.
Uncovering the Myth of Unbreakable Codes
If time has taught us anything, it is that people frequently do things that other people thought were impossible. Every time a new code or process is invented that is thought to be invincible, someone comes up with a method of breaking it.
FIGURE 7.3 Quantum cryptography being used to encrypt a message
The following list includes some common code-breaking techniques:
Frequency analysis Frequency analysis involves looking at blocks of an encrypted message to determine if any common patterns exist. Initially, the analyst doesn’t try to break the code but looks at the patterns in the message. In the English language, the letters e and t and words like the, and, that, it, and is are very common. Single letters that stand alone in a sentence are usually limited to a and I.
A determined cryptanalyst looks for these types of patterns and, over time, may be able to deduce the method used to encrypt the data. This process can sometimes be simple, or it may take a lot of effort.
Algorithm errors An algorithm is a method or set of instructions used to perform a task or instruction. In computers, algorithms are implemented in programs to perform repetitive operations. Sometimes complex algorithms produce unpredictable results; when discovered, the results can cause the entire encryption algorithm to be compromised. Cryptographic systems may have fundamental flaws in the way they’re designed. An error or flaw in either the design or the implementation of the steps can create a weakness in the entire coding system. This weakness may leave a coding system open to decryption regardless of the complexity of the algorithm or steps used to process the codes.
Brute-force attacks Brute-force attacks can be accomplished by applying every possible combination of characters that could be the key. For example, if you know that the key is three characters long, then you know that there is a finite number of possibilities that the key could be. Although it may take a long time to find the key, the key can be found.
Although it could take a long time to succeed with a brute-force attack, hackers use programs that run thousands of brute-force trial-and-error attempts in a short period of time.
Human error Human error is one of the major causes of encryption vulnerabilities. If an e-mail is sent using an encryption scheme, someone else may send it in the clear (unencrypted). If a cryptanalyst gets hold of both messages, the process of decoding future messages will be considerably easier. A code key might wind up in the wrong hands, giving insights into what the key consists of. Many systems have been broken as a result of these types of accidents.
A classic example involved the transmission of a sensitive military-related message using an encryption system. Most messages have a preamble that informs the receiver who the message is for, who sent it, how many characters are in the message, the date and time it was sent, and other pertinent information. In this case, the