This work is dedicated to the security of data stored on the hard drive of your computer and using encryption. The first part explains the basic concepts of cryptography and describes her in history. In other chapters, this work is dedicated to a description of the side channels and attacks on these channels. How can the attacker obtain information from a cryptographic module. The following section describes the types of encryption they use nowadays and what are their weaknesses. Bachelor thesis continues with examples of individual encryption programs and device ICZ Protect Boot. The last part deals with resistance testing on equipment ICZ Protect Boot. Testing of resistance to flow analysis using a side channel. Finally, bachelor thesis d...