COMPSCI 161
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CS 161 
Computer Security Project 2 
1 Sample Design 
Our design mimics the sample insecure client provided in the student framework. Our 
efficient update scheme is inspired by Merkle trees. As in the solutions to Part 1, when 
we encrypt something we always do an “authenticated encryption” by encrypting and then 
MACing the ciphertext. 
To initialize a client, we create a client encryption key and MACing key, and store them 
on the server encrypted under our public key. 
To create afile in...
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COMPSCI 161•COMPSCI 161
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CS 161 
Computer Security Project 2 
1 Sample Design 
Our design mimics the sample insecure client provided in the student framework. Our 
efficient update scheme is inspired by Merkle trees. As in the solutions to Part 1, when 
we encrypt something we always do an “authenticated encryption” by encrypting and then 
MACing the ciphertext. 
To initialize a client, we create a client encryption key and MACing key, and store them 
on the server encrypted under our public key. 
To create afile in...
Question 1 Behind the Scenes 
The vulnerability occurs in deja_vu function, where a malicious attacker can input more than 8 
characters, which will cause buffer overflow of buffer “door.” 
void deja_vu() 
{ 
 char door[8]; 
 gets(door); // where buffer overflow occurs 
} 
The info frame in the deja_vu function gives me this result: 
(gdb) i f 
Stack level 0, frame at 0xbffff800: 
 ... 
 Saved registers: 
 ebp at 0xbffff7f8, eip at 0xbffff7fc 
(gdb) p &door 
$1 = (char (*)[8]) 0xbffff7e8 
He...
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COMPSCI 161•COMPSCI 161
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Question 1 Behind the Scenes 
The vulnerability occurs in deja_vu function, where a malicious attacker can input more than 8 
characters, which will cause buffer overflow of buffer “door.” 
void deja_vu() 
{ 
 char door[8]; 
 gets(door); // where buffer overflow occurs 
} 
The info frame in the deja_vu function gives me this result: 
(gdb) i f 
Stack level 0, frame at 0xbffff800: 
 ... 
 Saved registers: 
 ebp at 0xbffff7f8, eip at 0xbffff7fc 
(gdb) p &door 
$1 = (char (*)[8]) 0xbffff7e8 
He...