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3.1.2. Pembahasan Proses IDEA
Proses penyelesaian metoda kriptografi IDEA ini dapat dibagi menjadi 3 tahapan yaitu:
1. Proses Pembentukan Kunci. 2. Proses Enkripsi.
3. Proses Dekripsi.
3.1.2.1. Proses Pembentukan Kunci
Metoda IDEA memiliki input 128 bit kunci key yang identik dengan 32 digit heksadesimal ataupun 16 karakter yang diproses untuk menghasilkan 52 buah subkey
dengan perincian masing-masing 6 buah subkey akan digunakan pada 8 putaran dan 4 buah subkey untuk transformasi output.
Untuk lebih memahami proses pembentukan kunci pada metoda IDEA, diberikan sebuah contoh berikut ini.
Misalkan : Input kunci = wayyantonosaings Proses pembentukan kuncinya adalah sebagai berikut :
KUNCI ENKRIPSI -----------------------------
PUTARAN - 1 INPUT KUNCI :
011101110110000101111001011110010110000101101110011101000110111101101 11001101111011100110110000101101001011011100110011101110011
Pecah menjadi 8 kelompok : KE1 Putaran 1 = 0111011101100001
KE2 Putaran 1 = 0111100101111001 KE3 Putaran 1 = 0110000101101110
KE4 Putaran 1 = 0111010001101111 KE5 Putaran 1 = 0110111001101111
KE6 Putaran 1 = 0111001101100001 KE1 Putaran 2 = 0110100101101110
KE2 Putaran 2 = 0110011101110011 PUTARAN - 2
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rotasi kiri 01110111011000010111100101111001011000010110111001110100011011110110
111001101111011100110110000101101001011011100110011101110011, 25 = 111100101100001011011100111010001101111011011100110111101110011011000
01011010010110111001100111011100110111011101100001011110010 Pecah menjadi 8 kelompok :
KE3 Putaran 2 = 1111001011000010 KE4 Putaran 2 = 1101110011101000
KE5 Putaran 2 = 1101111011011100 KE6 Putaran 2 = 1101111011100110
KE1 Putaran 3 = 1100001011010010 KE2 Putaran 3 = 1101110011001110
KE3 Putaran 3 = 1110011011101110 KE4 Putaran 3 = 1100001011110010
PUTARAN - 3 rotasi kiri
11110010110000101101110011101000110111101101110011011110111001101100 001011010010110111001100111011100110111011101100001011110010, 25 =
110100011011110110111001101111011100110110000101101001011011100110011 10111001101110111011000010111100101111001011000010110111001
Pecah menjadi 8 kelompok : KE5 Putaran 3 = 1101000110111101
KE6 Putaran 3 = 1011100110111101 KE1 Putaran 4 = 1100110110000101
KE2 Putaran 4 = 1010010110111001 KE3 Putaran 4 = 1001110111001101
KE4 Putaran 4 = 1101110110000101 KE5 Putaran 4 = 1110010111100101
KE6 Putaran 4 = 1000010110111001 PUTARAN - 4
rotasi kiri 11010001101111011011100110111101110011011000010110100101101110011001
110111001101110111011000010111100101111001011000010110111001, 25 = 011110111001101100001011010010110111001100111011100110111011101100001
01111001011110010110000101101110011101000110111101101110011 Pecah menjadi 8 kelompok :
KE1 Putaran 5 = 0111101110011011 KE2 Putaran 5 = 0000101101001011
KE3 Putaran 5 = 0111001100111011 KE4 Putaran 5 = 1001101110111011
KE5 Putaran 5 = 0000101111001011 KE6 Putaran 5 = 1100101100001011
KE1 Putaran 6 = 0111001110100011 KE2 Putaran 6 = 0111101101110011
PUTARAN - 5 rotasi kiri
01111011100110110000101101001011011100110011101110011011101110110000 101111001011110010110000101101110011101000110111101101110011, 25 =
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100101101110011001110111001101110111011000010111100101111001011000010 11011100111010001101111011011100110111101110011011000010110
Pecah menjadi 8 kelompok : KE3 Putaran 6 = 1001011011100110
KE4 Putaran 6 = 0111011100110111 KE5 Putaran 6 = 0111011000010111
KE6 Putaran 6 = 1001011110010110 KE1 Putaran 7 = 0001011011100111
KE2 Putaran 7 = 0100011011110110 KE3 Putaran 7 = 1110011011110111
KE4 Putaran 7 = 0011011000010110 PUTARAN - 6
rotasi kiri 10010110111001100111011100110111011101100001011110010111100101100001
011011100111010001101111011011100110111101110011011000010110, 25 = 011011101110110000101111001011110010110000101101110011101000110111101
10111001101111011100110110000101101001011011100110011101110 Pecah menjadi 8 kelompok :
KE5 Putaran 7 = 0110111011101100 KE6 Putaran 7 = 0010111100101111
KE1 Putaran 8 = 0010110000101101 KE2 Putaran 8 = 1100111010001101
KE3 Putaran 8 = 1110110111001101 KE4 Putaran 8 = 1110111001101100
KE5 Putaran 8 = 0010110100101101 KE6 Putaran 8 = 1100110011101110
PUTARAN - 7 rotasi kiri
01101110111011000010111100101111001011000010110111001110100011011110 110111001101111011100110110000101101001011011100110011101110, 25 =
010111100101100001011011100111010001101111011011100110111101110011011 00001011010010110111001100111011100110111011101100001011110
Pecah menjadi 8 kelompok 4 kelompok terakhir tidak digunakan : KE1 Transformasi Output = 0101111001011000
KE2 Transformasi Output = 0101101110011101 KE3 Transformasi Output = 0001101111011011
KE4 Transformasi Output = 1001101111011100
KUNCI DEKRIPSI -----------------------
KD1Putaran 1 = InverseKE1-Putaran9 = 0011110110000100 KD2Putaran 1 = MinusKE2-Putaran9 = 1110111110111000
KD3Putaran 1 = MinusKE3-Putaran9 = 1110110110101111 KD4Putaran 1 = InverseKE4-Putaran9 = 0000001010110111
KD5Putaran 1 = KE5-Putaran8 = 0000100011001000 KD6Putaran 1 = KE6-Putaran8 = 1010101001001001
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KD1Putaran 2 = InverseKE1-Putaran8 = 1111101000010101 KD2Putaran 2 = MinusKE3-Putaran8 = 1101011101111000
KD3Putaran 2 = MinusKE2-Putaran8 = 1101101111110111 KD4Putaran 2 = InverseKE4-Putaran8 = 1001011100110100
KD5Putaran 2 = KE5-Putaran7 = 0010100110101000 KD6Putaran 2 = KE6-Putaran7 = 1010101010001001
KD1Putaran 3 = InverseKE1-Putaran7 = 0011111111010101 KD2Putaran 3 = MinusKE3-Putaran7 = 1011101110101100
KD3Putaran 3 = MinusKE2-Putaran7 = 1111101101101100 KD4Putaran 3 = InverseKE4-Putaran7 = 0100010100111000
KD5Putaran 3 = KE5-Putaran6 = 1101010001010101 KD6Putaran 3 = KE6-Putaran6 = 0100010011110100
KD1Putaran 4 = InverseKE1-Putaran6 = 1000101001110000 KD2Putaran 4 = MinusKE3-Putaran6 = 1001101110101011
KD3Putaran 4 = MinusKE2-Putaran6 = 1011010111011110 KD4Putaran 4 = InverseKE4-Putaran6 = 1010001011101010
KD5Putaran 4 = KE5-Putaran5 = 0010101010100010 KD6Putaran 4 = KE6-Putaran5 = 0111101000100010
KD1Putaran 5 = InverseKE1-Putaran5 = 0101110011001110 KD2Putaran 5 = MinusKE3-Putaran5 = 1101010101101110
KD3Putaran 5 = MinusKE2-Putaran5 = 1111110111001110 KD4Putaran 5 = InverseKE4-Putaran5 = 0110110010001011
KD5Putaran 5 = KE5-Putaran4 = 0101000100111101 KD6Putaran 5 = KE6-Putaran4 = 0001000100000100
KD1Putaran 6 = InverseKE1-Putaran4 = 0001010011011111 KD2Putaran 6 = MinusKE3-Putaran4 = 1011011011011011
KD3Putaran 6 = MinusKE2-Putaran4 = 1110011011101011 KD4Putaran 6 = InverseKE4-Putaran4 = 0001001000101110
KD5Putaran 6 = KE5-Putaran3 = 1000000100100101 KD6Putaran 6 = KE6-Putaran3 = 0001000100010101
KD1Putaran 7 = InverseKE1-Putaran3 = 0000101101110011 KD2Putaran 7 = MinusKE3-Putaran3 = 0110110101100110
KD3Putaran 7 = MinusKE2-Putaran3 = 0111010101011100 KD4Putaran 7 = InverseKE4-Putaran3 = 1101010011001000
KD5Putaran 7 = KE5-Putaran2 = 1001001010001000
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KD6Putaran 7 = KE6-Putaran2 = 1000101010000010 KD1Putaran 8 = InverseKE1-Putaran2 = 0100000011001111
KD2Putaran 8 = MinusKE3-Putaran2 = 0110000101111000 KD3Putaran 8 = MinusKE2-Putaran2 = 1010110110110111
KD4Putaran 8 = InverseKE4-Putaran2 = 0100000111010110 KD5Putaran 8 = KE5-Putaran1 = 0100010001000101
KD6Putaran 8 = KE6-Putaran1 = 0100000100100000 KD1Putaran 9 = InverseKE1-Putaran1 = 0011001101110101
KD2Putaran 9 = MinusKE2-Putaran1 = 1010101110110001 KD3Putaran 9 = MinusKE3-Putaran1 = 1011101110111111
KD4Putaran 9 = InverseKE4-Putaran1 = 0111110001000101
3.1.2.2. Proses Enkripsi