- CryptoNugget
- Steganography
- Keys
- One Time Pad
- CDX-2
- Crack The Message For Cash!
- Further Reading
- About This Article
- Author Bio
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Crack The Message For Cash!
To illustrate the importance of cryptanalysis, I would like to offer a small cash prize to the first person to decrypt this message, encoded using a computer program to simulate a variation on a one-time pad. The plaintext message contains a telephone number. The first person to call that number and ask for Duplex will be sent the prize.
I used a very-slightly different algorithm for encryption than the classic one-time pad. Iβll play fair: hereβs my source code for encryption and decryption, which assumes the ASCII character set:
char addmod26(char a, char b)
{
char c;c = a - 'A';c += (b - 'A');if(c > 26)c -= 26;return c + 'A' - 1;
}
char submod26(char a, char b)
{
char c;c = 1 + a - 'A';c -= (b - 'A');if(c < 0)c += 26;return c + 'A';
}
void encrypt(char *p, char *k)
{
while(*p){*p = addmod26(*p, *k);p++, k++;}
}
void decrypt(char *c, char *k)
{
while(*c){*c = submod26(*c, *k);c++, k++;}
}
Here is the ciphertext:
NOWISTHETIMEFORALLGOODMENTOCOMETOTHEAIDOFTHEIRPARTY
It just happened to come out that way. Honest!
Now, Iβll play fairer than fair, and give you the one-time pad too!
FUZAVDKSZVYHRHCAOBYBPCWOUKAPGSHJRLUXFONHGCGSYYZEEGI
You now have all the information you need to decipher the message. Happy cracking!