With the wide spread of communications, demands for reliable and secure data transmission is growing. A reliable communication can be obtained via channel coding. Designing channel codes started in 1948 with Shannon’s theorem. In this theorem, it is proven that codes with rates arbitrarily close to the channel capacity exist with error decoding probability arbitrarily close to zero. In 1960, codes with sparse parity check matrices were introduced, but were mostly ignored in the next 30 years. These codes were re-discovered in the 1990’s and have been subject to many research projects. Some classes of these codes (e.g. QC-LDPC codes) have been used in standards in Mobile Wireless WAN. Secure transmission of data is achieved via cryptography. Although there exist many secure cryptosystems, a system which could combine encoding/encryption (decoding/decryption) would be very useful in communication systems. The first system of this kind was introduced by McEliece in 1978, known as the McEliece public key cryptosystem. The security of this system is based on the fact that, generally, decoding a linear code is a NP problem. In this system the bits of a plain-text are scrambled, bits of the codeword associated with it are permuted and some of them are randomly changed. Two main drawbacks of the McEliece cryptosystem is its large key size in order to hide the generator matrix of the applied code in the public key and low information rate. During the last 33 years many variants of the McEliece cryptosystem have been introduced; some have changed the code used in it, others have changed the structure of the scrambler and permutation matrices and some have changed the method of changing the bits of the codeword. But in all of these systems either one of the two problems remain unsolved or the cryptosystem has a low level of security. In this thesis a new symmetric key cryptosystem based on randomly puncturing a QC-LDPC code is proposed. A pseudo-random number generator is applied to determine which bits of a codeword should be punctured. One of the advantages of this cryptosystem is that with the absence of a permutation and scrambler matrices, the key size has been reduced and codes with rates as high as 0.875 can be used which also increases the information rate. Based on computer simulations of a parent code and its associated punctured code, suggested amounts of how many bits can be punctured is provided. It is shown that even with small amounts of punctures the system is secure. It is also shown that if an eavesdropper is provided with the code that is used, the system can remain secure. This is a unique characteristic that previous algebraic coded cryptosystems did not possess. In similar cryptosystems if the applied code is revealed, the system is broken. This is why the generator (or parity check matrix) of the applied code is part of the key (or part of the private key in public key algebraic coded cryptosystems). Key Words Coding, cryptography, LDPC codes, puncturing, pseudo-random number generator.