i KRIPTOGRAFI VISUAL DENGAN ALGORITMA ELGAMAL YANG

KRIPTOGRAFI VISUAL DENGAN ALGORITMA ELGAMAL
YANG DIMODIFIKASI UNTUK CITRA BERWARNA
DENGAN TIGA CITRA HASIL ENKRIPSI MENGGUNAKAN
PERANGKAT LUNAK MATLAB
Alexander Edi Suranta Kacaribu
Email: [email protected]
Jurusan Teknik Elektro, Fakultas Teknik
Universitas Kristen Maranatha
Jl. Prof. Drg. Suria Sumantri 65, Bandung 40164, Indonesia
ABSTRAK
Pada zaman modern ini, teknologi pengiriman pesan makin sering
digunakan. Tetapi apabila pesan yang ingin dikirimkan bersifat rahasia, maka pesan
tersebut harus dimodifikasi agar hanya dapat dimengerti oleh penerima yang dituju.
Hal ini dapat dilakukan dengan memakai kriptografi.
Algoritma ElGamal pertama kali diperkenalkan oleh Taher ElGamal pada
tahun 1985. Algoritma ini adalah algoritma kunci publik dan keamanannya terletak
pada kesulitan untuk mencari logaritma diskrit. Algoritma ElGamal telah sering
digunakan untuk mengenkripsi dan mendekripsikan text, email, file, dan software.
Pada tugas akhir ini, algoritma ElGamal akan digunakan sebagai algoritma
kriptografi visual untuk mengenkripsi dan mendekripsikan satu gambar. Pengujian
dilakukan dengan 4 citra berbeda. Dilakukan penilaian dengan MSE (Mean
Squared Error) untuk membandingkan citra awal dengan citra hasil dekripsi untuk
mendeteksi adanya error. Hasil dari pengujian MSE adalah 0 untuk semua citra.
Hal ini membuktikan bahwa citra awal dan citra hasil dekripsi mempunyai nilai
matrix yang sama.
Kata Kunci : kriptografi, kriptografi visual, elgamal, matlab
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VISUAL CRYPTOGRAPHY WITH MODIFIED ELGAMAL
ALGORITHM FOR COLORED IMAGE TO PRODUCE THREE
CIPHER IMAGES USING MATLAB
Alexander Edi Suranta Kacaribu
Email: [email protected]
Department of Electrical Engineering, Faculty of Engineering
Maranatha Christian University
Jl. Prof. Drg. Suria Sumantri 65, Bandung 40164, Indonesia
ABSTRACT
Nowadays, messaging technology more often used in daily life. But if the
message is confidential, it should be modified so that only can be understood by the
intended recipients. This can be done by using cryptography.
ElGamal algorithm was first introduced by Taher ElGamal in 1985. This
algorithm is public key algorithm and the security lies in the difficulty to find
discrete logarithm. ElGamal algorithm has often been used to encrypt and decrypt
a text, email, file and software.
In this final assignment, ElGamal algorithm will be used as algorithm of
visual cryptography to encrypt and decrypt a digital image. Tests will be conducted
with 4 different images. Assessment is conducted using MSE (Mean Squared Error)
to calculate the difference between the matrix of the initial image with the decrypted
image to detect if there are errors. The result of MSE are 0 for all images. This
proves that the initial images and the decrypted image has same matrix value.
Keyword : cryptography, visual cryptography, elgamal, matlab
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DAFTAR ISI
LEMBAR PENGESAHAN
PERNYATAAN ORISINALITAS LAPORAN
PERNYATAAN PUBLIKASI LAPORAN TUGAS AKHIR
KATA PENGANTAR
ABSTRAK................................................................................................................i
ABSTRACT.............................................................................................................ii
DAFTAR ISI ..........................................................................................................iii
DAFTAR GAMBAR ...............................................................................................v
DAFTAR TABEL...................................................................................................vi
BAB I PENDAHULUAN........................................................................................1
I.1 Latar Belakang........................................................................................1
I.2 Perumusan Masalah.................................................................................2
I.3 Tujuan Penelitian.....................................................................................2
I.4 Pembatasan Masalah...............................................................................2
I.5 Sistematika Pemahasan...........................................................................2
BAB II LANDASAN TEORI...................................................................................4
II.1 Kriptografi.............................................................................................4
II.1.1 Definisi dan Terminologi........................................................4
II.1.2 Prinsip Dasar Kriptografi[ ] ..................................................5
II.1.3 Jenis-Jenis Kriptografi............................................................6
II.2 Kriptografi Visual..................................................................................8
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II.3 Citra Digital.........................................................................................10
II.4 Algoritma ElGamal..............................................................................14
II.4.1 Besaran-Besaran dalam Algoritma Elgamal.........................14
II.4.2 Pembangkitan Kunci[ ] .......................................................15
II.4.3 Proses Enkripsi[ ] ................................................................15
II.4.4 Proses Dekripsi[ ] ................................................................17
II.5 Pengujian Gambar dengan MSE..........................................................18
BAB III PERANCANGAN DAN REALISASI.....................................................19
III.1 Perancangan Perangkat Lunak............................................................19
III.2 Pembangkitan Kunci...........................................................................20
III.3 Prosedur Proses Enkripsi....................................................................23
III.4 Prosedur Proses Dekripsi....................................................................27
BAB IV DATA PENGAMATAN DAN ANALISIS DATA..................................31
IV.1 Data Pengamatan................................................................................31
IV.2 Analisis Data......................................................................................34
BAB V KESIMPULAN DAN SARAN..................................................................35
V.1 Kesimpulan..........................................................................................35
V.2 Saran....................................................................................................35
DAFTAR PUSTAKA............................................................................................36
LAMPIRAN...........................................................................................................37
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DAFTAR GAMBAR
Gambar 2.1 Proses Enkripsi Menggunakan Kunci...................................................6
Gambar 2.2 Contoh Kriptografi Visual.....................................................................9
Gambar 2.3 Resolusi Citra......................................................................................11
Gambar 2.4 Visualisasi RGB..................................................................................13
Gambar 2.5 CMYK................................................................................................13
Gambar 2.6 Proses Pembangkitan Kunci................................................................15
Gambar 2.7 Skema Enkripsi Kriptografi Visual dengan Algoritma ElGamal yang
Telah Dimodifikasi.................................................................................................17
Gambar 2.8 Skema Dekripsi Kriptografi Visual dengan Algoritma ElGamal yang
Telah Dimodifikasi.................................................................................................18
Gambar 3.1 Diagram Blok Kriptografi Visual dengan Algoritma Elgamal dengan 3
Citra Hasil Enkripsi................................................................................................19
Gambar 3.2 Diagram Alir Proses Pembangkitan Kunci..........................................21
Gambar 3.3 Diagram Alir Proses Enkripsi..............................................................23
Gambar 3.4 Diagram Alir Subprocess Menghitung Rumus Enkripsi Algoritma
ElGamal.................................................................................................................24
Gambar 3.5 Diagram Alir Proses Enkripsi..............................................................27
Gambar 3.6 Diagram Alir Subprocess Menghitung Rumus Dekripsi Algoritma
ElGamal.................................................................................................................28
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DAFTAR TABEL
Tabel 2.1 Hubungan Antara Kedalaman Warna Dan Resolusi Warna....................12
Tabel 4.1 Citra Hasil Percobaan.............................................................................31
Tabel 4.2 Perbandingan Waktu Proses Program Terhadap Nilai p yang
Digunakan..............................................................................................................33
Tabel 4.3 Nilai MSE pada Setiap Percobaan...........................................................34
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