rsa-tool

Command line RSA tool written in C++, with use of the GMP library. Do not ever use this tool to transmit sensitive information. This tool is made to be a demonstration of RSA, but may not be entirely secure in practice.

Usage

1. Install the GNU MP Bignum Library.
2. Clone the git repository and navigate into its directory.

git clone https://github.com/JosCla/rsa-tool && cd rsa-tool

3. Build the program.

make

4. Run the program, providing usage flags to determine what the program does.

./rsa [flags]

Usage Flags

These flags determine what the program does, and what information it uses/outputs.

Mode Selection

Note: These three modes are mutually exclusive, and at least one must always be used.

• -g: Generate Key
  • Tries to generate a full RSA key from scratch, or from what information is given through -i flags.
• -e: Encrypt
  • Allows the user to encrypt information.
  • For this mode to function, e, n, and m must be provided through -i flags.
  • Note: If no output options are specified, -oc is effectively added by default.
• -d: Decrypt
  • Allows the user to decrypt information.
  • For this mode to function, d, n, and c must be provided through -i flags.
  • Note: If no output options are specified, -om is effectively added by default.

Input/Output Specifiers

Note: These flags can be added multiple times in a single command, in order to input from/output to multiple places.

• -i=FILENAME: Input properties from FILENAME
  • Inputs the properties from a given file to be used by the program.
  • Properties in the given file should be of the form:
    • @: 1234567890
  • with @ representing the corresponding qualifier (all input/output qualifiers listed below), and the numbers representing the value of the qualifier.
• -i*=...: Input a property manually
  • Lets the user input a certain property manually.
  • Putting a qualifier (all input/output qualifiers listed below) in place of the * denotes which property is being input.
    • ex. -ie=65537 sets the public key to 65537
• -o*: Output properties
  • Lets the user output properties to standard output.
  • Putting qualifiers (all input/output qualifiers listed below) in place of the * denotes which properties to output.
    • ex. -oen outputs the public key and the modulus
    • ex. -opqnted outputs all key properties
• -o*=FILENAME: Output properties to FILENAME
  • Lets the user output properties to a file.
  • Putting qualifiers (all input/output qualifiers listed below) in place of the * denotes which properties to output.
    • ex. -oen=pub.key -odn=priv.key outputs the public exponent and modulus to pub.key, and outputs the private exponent and modulus to priv.key
    • ex. -opqnted=cool.key outputs all key properties to cool.key

Input/Output Qualifiers

• p/q: primes used in key generation
• n: modulus
• t: totient of modulus
• e: public exponent
• d: private exponent
• m: message
• c: ciphertext
• s: message input/output in string form (converts to/from decimal to ASCII before inputting/outputting)

Other Usage Flags

• --e-len=...: Change generated e-length
  • Lets the user change the length of randomly generated public exponent e (default length 5).
    • ex. --e-len=50 makes randomly generated public exponents 50 digits long (in base-10)
• --pq-len=...: Change generated pq-length
  • Lets the user change the length of randomly generated large primes p and q (default length 200).
    • ex. --pq-len=500 makes randomly generated large primes 500 digits long (in base-10)