RSA-Common-Modulus-Attack is a Python 3 script to perform common modulus attacks on RSA. Given two ciphertext, encrypted with the same modulus N, but a different exponent e, it is possible to recover the plaintext of the message.
In order for this attack to work, the greatest common denominator of the two exponent should be 1 : gcd(e1, e2) = 1.
You can read more about this attack at https://medium.com/bugbountywriteup/rsa-attacks-common-modulus-7bdb34f331a5
I relied on Ashutosh Ahelleya's script for the math part : https://github.com/ashutosh1206/Crypton/blob/master/RSA-encryption/Attack-Common-Modulus/exploit.py
In order to run this script, you'll need to install some Python 3 modules.
git clone https://github.com/HexPandaa/RSA-Common-Modulus-Attack.git
cd RSA-Common-Modulus-Attack
pip3 install -r requirements.txtTo run the script, simply type the following command.
python3 rsa-cm.py -c1 <ciphertext1> -c2 <ciphertext2> -k1 <publickey1> -k2 <publickey2>
The output should be like so :
# ./rsa-cm.py -c1 message1.b64 -c2 message2.b64 -k1 key1.pub.pem -k2 key2.pub.pem [+] Recovered message: 6277601[...] [+] Recovered bytes: b'Yeah man[...]'
And finally the help message.
# rsa-cm.py -h usage: rsa-cm.py [-h] -c1 ciphertext1 -c2 ciphertext2 -k1 pubkey1 -k2 pubkey2 [-o outfile] A simple script to perform RSA common modulus attacks. optional arguments: -h, --help show this help message and exit -c1 ciphertext1 The first ciphered message -c2 ciphertext2 The second ciphered message -k1 pubkey1 The first public key -k2 pubkey2 The second public key -o outfile Output file More info at https://github.com/HexPandaa/RSA-Common-Modulus-Attack/
Happy hacking!