Encryption is often oversold as the solution to all security problems. However, there are threats that it does not address, but cryptography’s limitations are less recognized.
Time and power: Encryption may end up hogging a lot of time as well as power. The task of encryption as a whole is a time consuming one and it also takes 
up a lot of CPU cycles-this may retard system performance to a considerable extent, and if the pressure mounts, you stand to lose your entire data.
Poor usage: Encryption may lead you to a sense of false security. It’s not as if by encrypting the data, you can solve all your security problems. Make sure that you still pay enough attention to network and operating system security. Many users tend to disregard fundamental security practices for a file if it is encrypted. This becomes a security flaw because as we know, certain information should never be transmitted-encrypted or not. So it’s vital to remember that information security requires much more than just encryption. Make sure to always maintain the standard security procedure-authentication, configuration management, good design, access controls, firewalls, audting, security practices, and security awareness training.
Key length and cryptanalysis: Cryptanalysis is the study of trying to break ciphers. The most common method used by cryptanalysts is the brute force method.
Brute force means that the user tries all keys till the end result resembles estimated plain text. Given enough time and computing power, and/or special hardware, all key-based algorithms are theoretically breakable depending on the time and computing resources available. For example a 56-bit key algorithm broken in 1995 was said to have taken one week and about 120,000 processors
Encryption can be deceptive:
Encryption becomes redundant if the intruder is able to penetrate your system and access the plain text data directly from the stored files. Intruders can access memory contents by means of modifying network protocols, placing key loggers or using Trojans to get access to keys or plain text data or to completely subvert the encryption process. Also, be wary of rumors regarding encryption. Claims such as ‘encryption could stop computer crackers’ are false. Encryption does nothing to protect one against the many common methods of attack. These may include those that exploit bad default settings or vulnerabilities in network protocols or software.
Bugs: Finally, even with the strongest encryption algorithms, you can never be hundred percent sure that there are no loopholes or bugs. They are after all, codes which are bound to have alternate ways to hack, which might make passwords etc easy to hack. This in turn means that no matter how good your encryption is, the supposedly secured information can still be read
