A hybrid RSA-DH cipher for Signed Encrypted Messages

Although brute-force attacks on the modulus component of the RSA algorithm are possible, increasing the key size frustrates perpetrators more. However large keys increase CPU and Memory usage. Key handling would also be a challenge. Alternative approaches for strengthening the RSA algorithm are required. In addition, verification of message sources is not a feature of the RSA algorithm. Message senders cannot be tracked. If the RSA algorithm is to be used commercially, sender verification is necessary. The two drawbacks to commercial use of the RSA algorithm are, therefore, possibilities of attacks and lack of sender verification. The DH algorithm allows secure transmission of codes over insecure public channels. Can RSA encrypted messages be “signed” using DH generated codes? Can concatenation of DH codes and RSA encrypted messages detour brute force attacks while, at the same time, allowing message verification? We propose the design of a hybrid RSA-DH algorithm which signed encrypted messages are shared. The hybrid version satisfies most properties of good cryptosystems: confidentiality, integrity, availability, authenticity, and accountability. The results reported (CPU and memory usage) show negligible differences in the relative performance of the hybrid and ordinary versions, even when the hybrid version combines the processes of two algorithms.