Convergent Encryption and brute-force attack

brute_force.sh

# A simple Common Encryption dictionnary attack using OpenSSL
# ------------------------------------------------------------

# William Clot
# 09/01/2019

# Needs the following folders to work:
# - ./dict/ with the dictionnary files
# - ./data/user1...n with the encrypted files of each user using ./ce.sh

# A few styling colors and styles for output text
red=$(tput setaf 1)
green=$(tput setaf 2)
yellow=$(tput setaf 3)
endl=$(tput sgr0)

echo "${yellow} [-] Starting the brute-force attack${endl}"

total_files=0

print_success()
{
    echo "${green}$2 has the song $1 in his library${endl}"
    # Moving the decryption file to the corresponding user folder
    mv test_decryption "data/${2}/${1}"
    total_files=`expr $total_files + 1`
}

decryption_test()
{   # Function to test whether we can decrypt the message using a key
    message=$1
    key=$2
    file_name=$3
    user_name=$4

    if openssl aes-256-cbc -salt -in "$message" -out "test_decryption" -d -k "$key" 2> /dev/null; then
        # Decryption did work
        print_success $file_name $user_name
    fi
}

# Looping through all files in dictionnary
for dict_file in ./dict/*.mp3; do

    # Computing hash of file
    hash=$(cat $dict_file | openssl dgst -sha256)
    file_name=$(echo $dict_file | grep -oh "[a-zA-Z-]*.mp3")

    # Looping through each user
    for user in ./data/user*; do
        user_name=$(echo "$user" | grep -oh "user[0-9]*")
        # Looping through each file of user
        for encrypted_file in $user/*.enc; do
            decryption_test $encrypted_file $hash $file_name $user_name
        done
    done
done

rm test_decryption

echo "${yellow} Brute-force attack finished: ${total_files} files decrypted ${endl}"

convergent_encryption.sh

# Convergent Encryption
#----------------------

# William Clot
# 09/01/2019

if [[ $# -eq 0 ]] ; then
    echo 'Usage: ./ce.sh file'
    exit 0
fi

hash=$(cat $1 | openssl dgst -sha256)
echo "sha256 hash of $1: $hash"

openssl aes-256-cbc -salt -in $1 -out "$1.enc" -k $hash
echo "file $1 has been encrypted using it's hash as key"