The application of Blockchain technology has begun to be widely accommodated in industrial and business practitioner environments as a safeguard of transaction security so that now including the education sector, non-business institutions enjoy the use of this technology to support the learning process. Information on the protected Blockchain can be in the form of transactions, assets, identities, and other information packaged in digital form. Information is collected in the form of blocks that are interrelated by using the hash function as cryptographic encryption. This research uses Blockchain for online pocket money top-up transactions for students. The use of a centralized Blockchain is centralized to reduce server procurement costs, but to increase the security of transaction information, modification of each block series is carried out using the AES cryptographic approach. The results showed that the attack by inserting a Cross-Site Scripting (XSS) script if you want to know the value of the top-up transaction amount, you must be able to hack the cryptographic process. This is supported by chain validation testing to determine how many block changes have been changed.

Kriptografi pengubahan pesan asli menjadi disamarkan berguna menjaga kerahasiaan, integritas, keaslian, autentikasi pesan ketika proses komunikasi. Kriptografi klasik dengan subtitusi polialfabetik Vigenere memiliki tabel alphabet 26 baris yang relatif sederhana menjamin kerahasiaan. Kini pendekatan pembelajaran mesin Jaringan Syaraf Tiruan (JST) menjadi solusi layak untuk kriptografi dengan membentuk kunci rahasia dalam bobot jaringan sulit terpecahkan. Kunci dihasilkan dari bidirectional learning, dua pohon paritas saling tersinkronisasi dengan paramater hidden neuron, input neuron dan bobot. Sinkronisasi pada saluran publik dengan mengadopsi cara kerja Tree Parity Machine (TPM) dengan tipe feed forward. Pendekatan Kriptografi JST bermanfaat sebagai perlindungan dan serangan kriptografi. Penelitian ini memanfaatkan kombinasi sinkronisasi JST dan Vigenere dalam bentuk generator untuk optimasi pesan. Hasil pengujian kombinasi metode tidak berpengaruh dengan jumlah tampungan karakter pesan dan nilai parameter. Keunggulan kunci yang dihasilkan tidak bisa digunakan secara berulang meski nilai parameter sama, namun panjang karakter kunci berjumlah sama. Sisi fungsionalitas menghasilkan nilai 100%.   Kata kunci: Kriptografi, Jaringan Syaraf Tiruan (JST), Tree Parity Machine (TPM), Vigenere Cipher   Abstract Cryptography changes the original message to be disguised useful to maintain the security message. Vigenere polyalphabetic substitution relatively simple 26-row alphabetical table guaranteeing confidentiality. Machine learning approach Artificial Neural Network (ANN) becomes feasible solution for cryptography by forming secret key in the weight of the network that’s difficult to solve. The key’s generated from bidirectional learning, two parity trees synchronized with hidden neurons, input neurons, and weights. Synchronize public channels by adopting the work of Tree Parity Machine (TPM) with feedforward type. This research utilizes the combination of synchronization ANN and Vigenere from generators. The result of testing the combination of methods doesn’t affect the number of message character and parameter values. The advantages of the resulting key cannot be used repeatedly even though the parameter values ​​are the same, but the key length is the same number of characters. The functionality produces 100% value.   Keywords: Cryptography, Artificial Neural Networks (ANN), Tree Parity Machine (TPM), Vigenere Cipher

Information comes from a collection of data obtained from various sources that have been processed. An information can help in decision making, so it is considered to have a high effectiveness value for the recipient of the information. Information exchange that utilizes public media internet services is widely used, so the validity of information must be done security from unauthorized attacks. One of them uses cryptography. AES is a method used by the National Institute of Standards and Technology (NIST) as a standard for the United States Federal encryption algorithm. Creativity in cryptographic modification can increase the strength of an attack. This study uses AES 128, 192, and 256 bit CBC mode algorithms by conducting trials at the level of encryption, decryption and the appearance of character frequencies. Encryption test results obtained an average speed of 128 bit blocks, namely 14.2 ms, 256 bits 13.2 ms and 192 bits 11.5 ms. While the decryption test results obtained an average speed of 128 bit blocks, namely 13.2 ms, 192 bits 14 ms and 256 bits 16.5 ms. The pattern of occurrence of the average frequency generated by 9%, by accepting symbols and numbers using this algorithm has little to solve by reading the characters display. The validation test produces a value of 100% where the functionality testing shows the expected results.Keyword: Security Information, AES, CBC, AES Mode CBC Abstrak Informasi berasal dari sekumpulan data yang didapatkan dari berbagai sumber yang telah diolah. Sebuah informasi bisa membantu dalam pengambilan keputusan, sehingga dianggap memiliki nilai efektivitas tinggi bagi penerima informasi. Pertukaran informasi yang memanfaatkan layanan publik media internet marak digunakan, maka keabsahan informasi harus dilakukan keamanan dari serangan pihak tidak berwenang. Salah satunya menggunakan kriptografi. AES adalah metode yang dimanfaatkan National Institute of Standards and Technology (NIST) sebagai standar algoritma enkripsi Federal Amerika Serikat. Kreativitas dalam modifikasi kriptografi bisa meningkatkan kekuatan dari serangan. Penelitian ini menggunakan algoritma AES 128, 192, dan 256 bit mode CBC dengan melakukan uji coba pengujian pada tingkat kecepatan proses enkripsi, dekripsi dan kemunculan frekuensi karakter. Hasil uji coba pengujian enkripsi didapatkan tingkat kecepatan rata-rata blok 128 bit yaitu 14,2 ms, 256 bit 13,2 ms dan 192 bit 11,5 ms. Sedangkan hasil uji coba dekripsi didapatkan tingkat kecepatan rata-rata blok 128 bit yaitu 13,2 ms, 192 bit 14 ms dan 256 bit 16,5 ms. Pola kemunculan frekuensi rata-rata dihasilkan 9%, dengan menerima simbol dan angka menunjukan algoritma ini memiliki kemungkinan kecil dapat dipecahkan melalui pembacaan kemunculan karakternya. Pengujian validasi menghasilkan nilai 100% dimana pengujian fungsionalitas menunjukkan hasil yang sesuai diharapkan. Kata Kunci: Keamanan Informasi, AES, CBC, AES Mode CBC