DESIGN AND IMPLEMENTATION A NEW SECURITY HASH ALGORITHM BASED ON MD5 AND SHA-256

A cryptographic hash function has an important role in cryptography to achieve certain security goals such as authenticity, digital signatures, digital time stamping, and entity authentication. They are also strongly related to other important cryptographic tools such as block ciphers and pseudorandom functions .Due to the previous merits we present a proposal for a new secure hash algorithm based on the combination of some functions of SHA-256 (Secure Hash Algorithm 256) -with its message expansion modification- and MD5 (Message Digest 5) based on double-Davis-Mayer scheme to overcome the weakness existing in these functions. The proposal hash algorithm has been designed to satisfy the different levels of enhanced security and to resist the advanced hash attacks by increasing the complexity degree of the proposed hash algorithm. The security analysis of the proposed hash algorithm is compared to SHA256 and gives more security and highly acceptable results as shown in our security results and discussions.