This Attack Has Been Around for 20 Years — And It’s Back Again With The Bleichenbacher Oracle Attack on VPNs

Introduction

Bleichenbacher Oracle Attack

Bleichenbacher’s attack

0x00 0x02
import syse=79
d=1019
N=3337
def int_to_bytes(val, num_bytes):
return [(val & (0xff << pos*8)) >> pos*8 for pos in range(num_bytes)]
print '==Initial values ===='
print 'e=',e,'d=',d,'N=',N
print '\n============='

pad = '\x00\x02\x55\x55'
val = int(pad.encode('hex'), 16)
print 'Padding is:',pad,' Int:',val
cipher = val**e % Nprint 'Cipher is: ',cipherfor s in range(0,255):
cipher_dash = (cipher*(s**e)) % N
decode = cipher_dash **d % N
result = int_to_bytes(decode,2)
print s,
if (result[0]==0 and result[1]==2):
print '\n\\x00\\x02 Found it at s=',s
break
P=47 Q=71
n=P × Q = 13 × 11 = 3337
PHI = (p-1)(q-1) = 3220
e = 79
(79 × d) mod 3220 = 1 [Link]
d = 1019
Encryption key [3337,79]
Decryption key [3337,1019]
==Initial values ====
e= 79 d= 1019 N= 3337
=============
Padding is: �UU Int: 152917
Cipher is: 2652
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233
\x00\x02 Found it at s= 233

Conclusions

ASecuritySite: When Bob Met Alice

This publication brings together interesting articles related to cyber security.

Prof Bill Buchanan OBE

Written by

Prof at Napier. Serial innovator. Crypto Punk. Believer in fairness, justice & freedom. EU Citizen. Auld Reekie native. Old World Breaker. New World Creator.

ASecuritySite: When Bob Met Alice

This publication brings together interesting articles related to cyber security.