Enhancing Symmetric Encryption Using Digital Signatures

Abstract

Maintaining the confidentiality and integrity of digital documents transmitted through electronic media is a
critical security concern in the field of Information Security. To address this security concern, this paper
proposes a system that uses a digital signature to ensure the authenticity, non-repudiation and integrity of the
transmitted data and it also uses symmetric encryption to provide authentication and confidentiality of the
transmitted data. The Rivest, Shamir & Adleman (RSA) algorithm was used to implement the Digital Signature
while the Advanced Encryption Standard (AES) was used for symmetric encryption. The system involves
encrypting a plaintext using AES, then a hash function (SHA-256) is used to create a hash value of the
ciphertext and the private key of the RSA algorithm is used to encrypt the hash value to produce the digital
signature. The ciphertext and the digital signature are attached and sent to the recipient. The digital signature is
decrypted by the recipient to obtain the hash value of the ciphertext, then it verifies if it is a valid signature
before proceeding to decrypt the ciphertext using the AES secret key. The proposed system was evaluated
against the existing AES algorithm. The size of the test file was observed and analyzed before and after
encryption, this showed that the size did not change. Different RSA key sizes were used to perform signature
and verification processes to see how long it takes to perform the operations, this also showed that the smaller
the key size the faster the signature and verification processes and the verification process is a much faster
process than the signature process. The system was able to meet the cryptography objectives and will be useful
to individuals and businesses in transmitting sensitive information over insecure communication mediums.