▶ 8.5 Data Integrity and Digital Signatures
Consider the following:
Bob borrows $3 from Kevin. Bob writes himself a reminder note that says “I owe Kevin $3.” He saves it in a file on his USB drive. Bob encrypts the file with RC4 or some other stream cipher.
A week later he pays back the $3. Before he deletes the note, he looks at it again. Now it says “I owe Kevin $7.”
If Kevin knows exactly what the file says, he can change its contents bit by bit without knowing the encryption key. This is sometimes called the bit-flipping attack (FIGURE 8.18).
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