adiwajshing / SimpleCrypto

All coding work done for Ashoka University CS-2362

ElGamal (HW4 4.5)

Please refer to ElGamalSign.c for all signing, sign verification & existential forgery function implementations. I'm using this library for the SHA256 hashing.

1. To sign something, use uint8_t *ElGamal_signature (const uint8_t *plaintext, size_t *len, mpz_t g, mpz_t a, mpz_t q, int hash_sha256).
2. To verify a signature, use int ElGamal_sign_verify (const uint8_t *plaintext, size_t plaintextlen, const uint8_t *sign, mpz_t h, mpz_t q, mpz_t g, int hash_sha256).
3. To generate an existential forgery, use void ElGamal_generate_existential_forge (mpz_t r, mpz_t s, mpz_t m, mpz_t h, mpz_t q, mpz_t g, unsigned long seed).
4. For a test of the signing, sign verification & existential forgery, please refer to testElGamal() in ElGamal.c.
5. For a small demo of signing & verification, please refer to ElGamalProgram.c.
6. To compile, you will need GMP installed on your system. Given this, the build system is Xcode so all you need to do is open the Crypto.xcodeproj file with Xcode and click Run. This will run the ElGamal encryption/decryption/signing demo along with the curve tests.

Curve (HW4 4.4)

Please refer to Curve.h & Curve.c for all curve construction & arithmetic implementations. Please refer to CurveTest.c for unit tests of curve arithmetic.

The curve can be setup either as an M-221 curve or a P-192 curve.

1. The syntax for the Curve library is very similar to the GMP syntax. Examples include:
   • To init from a string, mpz_init_set_str(ptr, "12312", 10) becomes curve_init_set_str(curvePtr, "12312", "312123", 10)
   • To add, mpz_add(result, ptr1, ptr2) becomes curve_add(result, curvePtr1, curvePtr1)
   • To multiply, mpz_mul(result, ptr1, ptr2) becomes curve_mul(result, curvePtr, k) And so on, please see Curve.h for a list of all the functions.
2. The main program runs the Curve Test suite. This can also be called via the curve_test() function imported from Curve.h.
3. Each function in Curve.h has a comment above it pointing to the correct question part.
4. The Curve functions are tested on the P-192 curve using test vectors from here.
5. The project includes all header & source files. Though, to compile, you will need GMP installed on your system. Given this, the build system is Xcode so all you need to do is open the Crypto.xcodeproj file with Xcode and click Run. This will run the curve test suite.
6. There are no known issues with the code.

ElGamal (HW3 3.10)

To view the implementation of ElGamal, please refer to ElGamal.h & ElGamal.c. There is also a unit test present in the files. It can work with 300 or 512 bit modes. However, for a simple example, please refer to ElGamalProgram.c.

RSA (HW3 3.9)

To run any RSA related function, please ensure that you have the GMP library installed on your computer. I have also provided a complied binary in the project (RSAProgram) to run what is required of in the question. However, if you so wish to see the code please refer to RSAProgram.c for the running, ASN1.h & ASN1.c for the implentation of the ASN.1 protocol, RSA.h & RSA.c for the implementation of RSA. The program, by default uses RSA 1024, however, it can be recomplied for RSA 512 or RSA 2048 as well. A unit test for RSA are also present in RSA.c

1. To generate keys, call ./RSAProgram -keygenerator
2. To encrypt plaintext.txt, call ./RSAProgram -encrypt
3. To decrypt ciphertext.txt, call ./RSAProgram -decrypt.

The benchmarks for different versions of RSA are the following:

RSA 1024

1. time taken: 0.004163
2. time taken: 0.004677
3. time taken: 0.010959
4. time taken: 0.009929
5. time taken: 0.021239
6. time taken: 0.011216
7. time taken: 0.015868
8. time taken: 0.008040
9. time taken: 0.005892
10. time taken: 0.020896

average time: 0.011288

RSA 2048

1. time taken: 0.122571
2. time taken: 0.094352
3. time taken: 0.120993
4. time taken: 0.085912
5. time taken: 0.052626
6. time taken: 0.063667
7. time taken: 0.059860
8. time taken: 0.088416
9. time taken: 0.137585
10. time taken: 0.085261

average time: 0.091124

RSA 4096

1. time taken: 0.620837
2. time taken: 0.806106
3. time taken: 1.491062
4. time taken: 0.837068
5. time taken: 1.649042
6. time taken: 1.519799
7. time taken: 5.413277
8. time taken: 0.892993
9. time taken: 1.117289
10. time taken: 1.403269

average time: 1.575074

DES

For HW2 2.7

I initially wrote the vanilla DES algorithm with CBC chaining & PKCS5 padding with all the permutations (see DES.h & DES.c).

To encrypt using vanilla DES, call des_cbc_encrypt(plaintext, &len, key, iv), where:

plaintext is the pointer to the byte array you want to encrypt.

len is the parameter for the length (pass a reference to it, as the function will update the length of the text if padding was added)

key is the 8 byte key

iv is the 8 byte long IV (provide NULL to use without CBC chaining, i.e. ECB mode)

For decryption, call des_cbc_decrypt(ciphertext, &len, key, iv) , same arguments apply.

To use the variation of DES mentioned in the question, I simply swapped out the sub key generation function & the feistel network function (see VDES.h & VDES.c).

To encrypt a piece of text using this variation of DES (VDES), call vdes_encrypt(plaintext, &len, key, iv) . The only difference in the arguments being passed is that the key is 7 bytes long.

For decryption, call vdes_decrypt(ciphertext, &len, key, iv) .

To run the program:

1. include VDES.h in your main file (VDES => Variation DES)
2. to run the program in encryption mode: call run_vdes_encrypt()
3. to run the program in decryption mode: call run_vdes_decrypt()

For HW2 2.8

I encrypt the plaintext using the variation of DES mentioned the previous question in CBC mode and then using DES in ECB mode. (See DDES.h & DDES.c)

To encrypt using D-DES, call ddes_encrypt(plaintext, &len, K1, K, K2) the function takes in a pointer to the byte array you want to encrypt, a parameter for the length (pass a reference to it, as the function will update the length of the text if padding was added), a 7 byte long key (K1), an 8 byte long K, and another 7 byte long key (K2).

For decryption, call ddes_decrypt(ciphertext, &len, K1, K, K2) , same arguments apply.

AES

For HW2 2.4

See AES.h & AES.c and run testAES(); to run the encrypt the plaintext using the key mentioned in the template in AES 128 mode. To generally use AES encryption, you can call aes_cbc_encrypt (plaintext, &len, key, iv, mode) where:

plaintext is the pointer to the byte array you want to encrypt.

len is the parameter for the length (pass a reference to it, as the function will update the length of the text if padding was added)

key is the key (16 bytes for AES 128, 24 bytes for AES 192, 32 bytes for AES 256)

iv is the IV (provide NULL to use without CBC chaining, i.e. ECB mode)

mode is the AES mode ==> AES_128, AES_192, AES_256

For decryption, you can call aes_cbc_decrypt (ciphertext, &len, key, iv, mode) where the same arguments apply except the first parameter is the ciphertext you want to decrypt.

Note: the mix_columns() step was not present in the template, however, I have implemented it.