Quantum key distribution (QKD) is a technique for distributing symmetric encryption keys securely using quantum physics. The rate of key distribution is low and decreases exponentially with increasing distance. A classic trusted relay (CTR) uses additional keys to enhance security distance in QKD networks. To ensure secured data transmission there are several techniques being followed. One among them is cryptography which is the practice and study of hiding information. The proposed method is Back Track-ASCII algorithm, this is a new cryptographic algorithm which is used for secure the data in cloud. Encryption and decryption require the use of some secret information, usually referred to as a hash key. In particular, a novel survivability model called software defined quantum key relay failure (SDQKRF) is proposed in this paper in which a new function is developed and added to the SDN controller. According to the simulation results, SDN over a QKD network using the SDQKRF model is more reliable and performs better in terms of the key generation ratio ECC algorithm is used to generate the key. The data to be encrypted is called as plain text. The plain text is converted into ASCII code, which is added to ASCII code of cover message which is generated by Backtrack algorithm, also the key is added to these. The encrypted data obtained as a result of encryption process is called as cipher text. Depending on the encryption mechanism used, the same key might be used for both encryption and decryption, while for other mechanisms, the keys used for encryption and decryption might be different. Each encryption algorithm can be decrypted within sufficient time and with sufficient resources. The possibility of decryption has increased with the development of computer technology since available computer speeds enable the decryption process based on the exhaustive data search. This has led to the development of steganography, a science which attempts to hide the very existence of confidential information. Hence, a new method which combines the favourable properties of cryptography based on substitution encryption and stenography is analysed in the paper. INDEX TERMS: Quantum key distribution (QKD), software-defined network (SDN), survivability, classical trusted relay (CTR).