Symmetric Stream Cipher using Triple Transposition Key Method and Base64 Algorithm for Security Improvement

Symmetric type cryptography algorithm is known many weaknesses in encryption process compared with asymmetric type algorithm, symmetric stream cipher are algorithm that works on XOR process between plaintext and key, to improve the security of symmetric stream cipher algorithm done improvisation by using Triple Transposition Key which developed from Transposition Cipher and also use Base64 algorithm for encryption ending process, and from experiment the ciphertext that produced good enough and very random.


Introduction
Data security is very important in maintaining the confidentiality of information, especially containing sensitive information that should only be known by a particular party, especially if the delivery is arranged through the public network, if the data is not secured it will be easy to tap and known contents Information by unauthorized parties [1] [2]. One of the ways used to secure data is to use the cryptographic system by encoding the substance of the information (plaintext) into the contents that are not understood through the encryption process and to recover the original information using the decryption process by using the correct key [1].
The symmetric stream cipher method in this research uses triple transposition key and Base64 algorithm to increase the security of symmetric stream cipher algorithm. Improvisation performs on symmetric stream cipher method, in this study received two key types namely the main key and Private Crypto Code. With the result forming three transposition keys containing 463, 251, 181 loop which is interconnected due to feedback output from key processing. With the method of the symmetric stream, cipher will produce output with high speed and have Private Crypto Code.

Theory
A. Symmetric Stream Cipher A stream cipher is a type of symmetry encryption algorithm that is much faster than any block cipher algorithm, and stream ciphers are used for smaller data blocks in bit sizes [3] In transposition cipher, plaintext remains the same, but the order is changed. In other words, this algorithm transfers the character set inside the text. Another name for this method is the permutation [6] because transposed each character in the text is the same as doing the character of the characters, in the results of this study the authors to improvise transposition algorithm that is named Triple Transposition Key specifically used to generate keys [6]. Triple Transposition Key is a technique used to form keys of 463, 251, and 181 which is connected because of the feedback output of key processing, the Triple Transposition Key process that the author uses is as follows: Encodebyte= a byte XOR FnULTRA(FEEDBACK) FEEDBACK=EncodeByte Keys that have been formed then combined using the following functions: Output = (OUT1 + OUT2 + OUT3) Mod 256 C. Base64 Algorithm The Base64 transformation is one of the algorithms for encoding and decoding data in ASCII format, which are based on the number 64. The character generated from Base64 consists of A-Z, a-z and 0...9, plus the last two characters of / and + [7].

Proposed Method
In this experiment data security is perform using stream cipher algorithm, and the key utilized in the encryption process consists of the primary key and Private Crypto Code and then process with Triple Transposition Key algorithm, and next step is encryption string with Symmetric Stream Cipher, and Base64 algorithm, the use of 2 keys in the encryption process is expected to be able gives better ciphertext results.
The process of completion of cryptography method Symmetric Stream Cipher can be divide into three parts, such as: a. Key  The result of K1 above is the outcome of the process of Triple Transposition Key 462, for keys with 251 and 181 also in the same way to obtain a different result, and each result will combine with function (OUT1 + OUT2 + OUT3) Mod 256 to get a key.

Conclusion
Conclusion on the results of this study, the addition of security to Symmetric Stream Cipher with Triple Transposition Key and Base64 produce a ciphertext that is very random and not easily penetrated even with some techniques commonly used by cryptanalyst because the encryption process has some fairly complicated process let alone the key used Raised with the Triple Transposition Key used by the author.