On the Application of Noiseless Steganography and Elliptic Curves Cryptography Digital Signature Algorithm Methods in Securing Text Messages

Elliptic curve cryptography includes symmetric key cryptography systems that base their security on mathematical problems of elliptic curves. There are several ways that can be used to define the elliptic curve equation that depends on the infinite field used, one of which is the infinite field prima ( F P where p > 3 ). Elliptic curve cryptography can be used for multiple protocol purposes, digital signatures, and encryption schemes. The purpose of this study is to determine the process of hiding encrypted messages using the Noiseless Steganography method as well as the generation of private keys and public keys and the process of verifying the validity of the Elliptic Curves Cryptography Digital Signature Algorithm (ECDSA). The result of this thesis is that a line graph is obtained that store or hides a message using the steganography method and a message authenticity from the process of key generation and verification of validity using the ECDSA method. By selecting three samples consisting of one test sample and two differentiating samples, a line graph, an MD5 hash value, and a value at the point are obtained M(r, s) different. Successively obtained values M(r, s) to message “Matematika 2018”, “MATEMATIKA 2018”, and “2018 matematika” are M(94,67), M(15,17), and M(9,16) . The discussion in this thesis only covers the elliptic curves on prime finite field. So, for the next thesis, the next researcher can do a discussion about the elliptic curve on the finite field (F 2 m ) or the application of elliptic curve cryptography and other steganography methods.


INTRODUCTION
The form of communication in this era has gone through several stages of development. This can be clearly seen from the way people use various digital devices as a means of communication. Thanks to digital communication devices, people can communicate remotely through voice, text, images, and video. Different types of messages sent only to certain parties are confidential. Therefore, in sending a message or information, it is necessary to pay attention to its authenticity or authenticity so that the message you want to convey is received by the right person an algorithm is needed to maintain the authenticity of the message or information, namely Elliptic Curves Cryptography Digital Signature Algorithm [1], [2]. A cryptographic value that depends on the message body and the sender of the message is called a digital signature or digital signature. Digital signatures generate different signatures on each document. It is a digital signature taken from the document itself [3]. Basically, the use of digital signature functions the same as signatures in printed documents, namely as a process for authentication [4]. The use of a digital signature combines two cryptographic algorithms at once, namely the first one-way hash function algorithm that will produce a message digest, and the second algorithm is the public key algorithm used to encrypt the message digest.
A hash function is a function that accepts an arbitrary-length string input and then compresses it into a fixed-sized message digest [5]. One of the one-way hash functions used is MD5 (message digest 5) which is an improvement over MD4 [6]. Broadly speaking, md5 manufacturing has four steps, namely the addition of bits of the blocker, the addition of the original message length value, initialization of the MD buffer, and message processing [7]. The public key algorithm in its implementation uses a pair of keys that are a public key that can be deployed, and a private key known to the owner only. Elliptic Curve Cryptography (ECC) is cryptography that operates on elliptic curve domains. In the process of working on cryptographic algorithms, elliptic curves require mathematical concepts, namely abstract algebra including group theory, rings, and fields [8]. In addition to abstract algebraic concepts, there is a theory of numbers, especially in the modular concept of arithmetic. In the application of cryptography, one of them is the elliptic curve digital signature algorithm or elliptic Curve digital Signature algorithm which is based on the ElGamal Signature algorithm. The result of this algorithm is in the form of the authenticity of a message M.
The method for keeping a message confidential is not just by using cryptography [9]. Another technique that can be used besides cryptography is steganography [10]. Steganography can be viewed as a complement to cryptography because they complement each other. The security of a message can be improved by combining cryptography and steganography [11]. In general, the technique used is to encrypt messages first with cryptographic algorithms, then encrypted messages are hidden in other media (voice, text, video, and images) by steganography methods [12]. If the concealment of the message on conventional steganography can degrade the quality of the cover, then the concealment of the message on the Noiseless Steganography or NoStega methods does not cause damage. Some research on elliptic curve cryptography has been done by Annisa Hardiningsih HR, creation and verification of digital signatures using the MD5 hash function and the RSA algorithm cryptography on a document. The results show that each electronic document produces a different signature, even though it is signed by the same person and electronic documents that have not changed their contents result in the decryption value of the digital signature and message digest modulo n of the same value [13].
In previous studies has been discussed related elliptic curve cryptography and is given a simple example of the use of elliptic curve cryptography in the ElGamal encoding process to make it easier to understand [14]. The study only discussed the application of elliptic curve cryptography to the ElGamal encoding process only and was limited to finite fields F p .

On the Application of Noiseless Steganography and Elliptic Curves Cryptography Digital Signature Algorithm Methods in Securing Text Messages
Juhari 485 In previous studies discusses the level of security and performance of cryptographic algorithms Elliptic Curves Cryptography Digital Signature Algorithm (ECDSA) or algorithms Rivest-Shamir-Adleman (RSA) [15]. So that this research will be carried out a combination of cryptography and steganography methods without the need for a cover to hide the message. The steganography method used is Noiseless Steganography (NoStega) and the cryptographic method used is the Elliptic Curves Cryptography Digital Signature Algorithm (ECDSA).

METHOD
The stages of this study consist of five steps. The steps are as follows: 1. Represents message into 8-bit ASCII code. 2. Perform a message concealment using the Steganography method.

Application of Steganography Method to a Message
Change a message = " Matematika 2018" to a binary representation (each character is converted into an 8-bit ASCII code) to 01001101 01100001 01110100 01100101 01101101 01100001 01110100 01101001 01101011 01100001 00100000 00110010 00110000 00110001 00111000 Next, it will be converted back the above bit groups to decimal values 77 97 116 101 109 97 116 105 107 97 32 50 48 49 56 Then a graph will be made using the decimal value above, for example, the value states the number of COVID-19 cases in Pasuruan Regency.    (1,3). Not all ∈ 97 will generate a value 2 of elements 97 . For example, for = 0 obtained value 2 = 0 3 + 0 + 3 ( 97) = 3, While 2 not contained on 97 . So, for = 0 no value that filled. Of the 96 points of the curve that exist, it turns out that all of these points are generators of the elliptic group (97).

Elliptic Curves Cryptography Digital Signature Algorithm
There are three digital signature elliptic curve algorithms used: . If = 0, then repeat to the stage 1.

CONCLUSION
The steganography method can be used to hide a secret message in another message as a cover so that the existence of the secret message cannot be detected. As well as the use of the Elliptic Curves Digital Signature Algorithm method on a message to identify or authenticate the authenticity of a message sent and received correctly from the real sender and recipient.