This master thesis is related to the error processing stage of a practical quantum communication system.The system allows secure communications between two parties, (Alice and Bob). Initially, Alice has a string of bits that wants to send to Bob in a safe way. In order to do this, Alice encrypts the string of bits using photons that are polarized through applying horizontal, vertical, diagonal left and diagonal right bases. When all photons have been polarized, Alice sends them through a quantum channel to Bob. Once Bob receives them, he applies the same type of bases that Alice uses to encrypt for decrypting but in a random manner. They then compare the bases they used through a public, but authenticated channel, and keep only those in which both use the same bases for encryption and decryption. This string of bits, known as the sifted key, can still contain errors (bits that are different for Alice and Bob) which are produced by the noise of the channel or because Bob has applied a wrong basis in one or more photons. To resolve this, Alice and Bob use a reconciliation protocol which allows to fix the errors of the sifted key that Bob has. In this reconciliation protocol, Bob divides his key in blocks. For each block, Bob calculates the parity and asks Alice for the parity of the corresponding block in Alice's key. When Bob receives Alice’s parity, he compares it with his parity for the current block. If the parties are not equal, there is an error in the current block. In this case, Bob will look for the error in the block and fix it.However, there can be an eavesdropper (Eve) in the communications who can try to steal information. In this case, during quantum communications, Eve can intercept the photons that Alice has sent to Bob and can do the following:1. Decrypt the key that Alice has sent to Bob using the same bases that Alice. Eve has ¼ of probability of success and ¾ probability of failing. If Eve chooses this option, she will modify the state of each photon.2. Save the photons state without measuring anything and waiting to finish the photon transmissions.(Truncated by viXra Admin)