i want to conver this piece of code written in C to C#

Question

// Provides the key generation functions //MAX and MIN values for random numbers unsigned int MAX=256; unsigned int MIN=1; //function to calculate the multiplicative inverse of e mod r using the extended Euclidean algorithm int gencongrel (unsigned int e unsigned int r) { long temp u v quotient previous_u previous_v; u = 0; previous_u = 1; v = 1; previous_v = 0; while (r != 0) //keep calculating until it reaches 0 { temp = r; //store the old value quotient = e / r; //quotient of e and r r = e % r; //calculate the new value e mod r e = temp; //restore the old value temp = u; //store the old value u = previous_u - quotient * u; //calculate the new u using the previous one and quotient previous_u = temp; //restore the old value temp = v; //store the old value v = previous_v - quotient * v; //calculate the new v using the previous one and exponent previous_v = temp; //restore the old value } return (previous_u); } //function to calculate the greatest common denominator of two numbers using the Euclidean algorithm int gcd(unsigned int number unsigned int r) { unsigned int temp; while (r != 0 ) //keep calculating until it reaches 0 { temp = r; //store the old value r = number % r; //calculate the new value number mod r number = temp; //restore the old value } return number; } //function to generate a number coprime to r called from gen_keys int gencoprime(unsigned int r) { unsigned int number; do { do //Generate a random number between MIN and MAX { number = rand() % MAX; } while (number } while (gcd(number r) != 1); //keep generating numbers until the gcd of the generated number and r is 1 return (number); } //function to generate prime numbers called from gen_keys int genprime (void) { unsigned int modulus modulus_squared prime number result; prime = 0; //Assume the number is not prime result = 0; while (prime == 0) //While it is not prime { modulus = 2; //Can start at 2 dividing by 1 not needed modulus_squared = 4; do //Generate a random number between MIN and MAX { number=rand() % MAX; } while (number while (modulus_squared root of the number { result = number % modulus; //The result is the remainder after dividing the number by the current modulus if (result == 0) //If the remainder is 0 { prime = 0; //The number is not prime break; } modulus_squared = modulus * modulus; if (modulus == 2) //If the current modulus is 2 { modulus++; //Add one to make next modulus 3 } else { modulus++; //Otherwise add 2 to keep modulus odd modulus++; } } if (result != 0) //If the result is 0 when divided by all numbers up to the square root of the number { prime = 1; //Number must be prime } } return (number); } //key generation function called from menu.c int gen_keys (void) { unsigned int p q e n r; long d; int error; srand(time(NULL)); //randomise the random number generator error = 1; do //generate two different prime numbers { p = genprime(); q = genprime(); } while (q == p); n = p * q; //n is the product of p and q r = (p - 1) * (q - 1); //r is the totient of p and q e = gencoprime(r); //e is coprime to r d = gencongrel(e r); //d is the multiplicative inverse of e mod r if (d { d = d + r; //d must be positive so calculate d + r to get d mod r } //Write the key files FILE *fptr; fptr = fopen(private_key.txtw); if (fptr != NULL) //check the file was opened correctly { fprintf(fptr%ld %d
 d n); //write the values fflush(fptr); fclose(fptr); error = 0; } fptr = fopen(public_key.txtw); if ((fptr != NULL) || (error == 0)) //check the file was opened correctly fprintf(fptr%d %d
 e n); //write the values out fflush(fptr); fclose(fptr); error = 0; } else { error = 1; } if (error == 0) { printf(
KEY GENERATION SUCCESSFULL

); //if there wasn't an error } else { printf(
ERROR: KEY GENERATION UNSUCCESSFULL

); //if there was an error return(1); } return(0); }

Vulpes · Answer

OK. I've had a go at translating this. It seems to be working but I'd check it carefully. I've used the C# equivalent of the C types in nearly all cases even though this means a lot of explicit conversions in C#. As C# doesn't support global functions I've made them all static methods of a static class called KeyGenerator. I've also added a Program class to test it. using System; using System.IO; public static class KeyGenerator { // Provides the key generation functions // MAX and MIN values for random numbers private const uint MAX = 256; private const uint MIN = 1; // add const for RAND_MAX private const int RAND_MAX = 0x7FFF; // add field for Random object // uses a time based seed private static Random random = new Random(); // function to calculate the multiplicative inverse of e mod r using the // extended Euclidean algorithm public static int gencongrel (uint e uint r) { int temp u v quotient previous_u previous_v; u = 0; previous_u = 1; v = 1; previous_v = 0; while (r != 0) //keep calculating until it reaches 0 { temp = (int)r; //store the old value quotient = (int)(e / r); //quotient of e and r r = e % r; //calculate the new value e mod r e = (uint)temp; //restore the old value temp = u; //store the old value u = previous_u - quotient * u; //calculate the new u using the previous one and quotient previous_u = temp; //restore the old value temp = v; //store the old value v = previous_v - quotient * v; //calculate the new v using the previous one and exponent previous_v = temp; //restore the old value } return previous_u; } // function to calculate the greatest common denominator of two numbers // using the Euclidean algorithm public static int gcd(uint number uint r) { uint temp; while (r != 0 ) //keep calculating until it reaches 0 { temp = r; //store the old value r = number % r; //calculate the new value number mod r number = temp; //restore the old value } return (int)number; } //function to generate a number coprime to r called from gen_keys public static int gencoprime(uint r) { uint number; do { do //Generate a random number between MIN and MAX { number = (uint)(rand() % MAX); } while (number } while (gcd(number r) != 1); //keep generating numbers until the gcd of the generated number and r is 1 return (int)number; } //function to generate prime numbers called from gen_keys public static int genprime () { uint modulus modulus_squared prime number = 0 result; prime = 0; //Assume the number is not prime result = 0; while (prime == 0) //While it is not prime { modulus = 2; //Can start at 2 dividing by 1 not needed modulus_squared = 4; do //Generate a random number between MIN and MAX { number= (uint)(rand() % MAX); } while (number while (modulus_squared { result = number % modulus; //The result is the remainder after dividing the number by the current modulus if (result == 0) //If the remainder is 0 { prime = 0; //The number is not prime break; } modulus_squared = modulus * modulus; if (modulus == 2) //If the current modulus is 2 { modulus++; //Add one to make next modulus 3 } else { modulus++; //Otherwise add 2 to keep modulus odd modulus++; } } if (result != 0) //If the result is 0 when divided by all numbers up to the square root of the number { prime = 1; //Number must be prime } } return (int)number; } //key generation function called from menu.c public static int gen_keys () { uint p q e n r; int d; int error; /* NO NEED FOR srand */ error = 1; do //generate two different prime numbers { p = (uint)genprime(); q = (uint)genprime(); } while (q == p); n = p * q; //n is the product of p and q r = (p - 1) * (q - 1); //r is the totient of p and q e = (uint)gencoprime(r); //e is coprime to r d = gencongrel(e r); //d is the multiplicative inverse of e mod r if (d { d = (int)(d + r); //d must be positive so calculate d + r to get d mod r } //Write the key files try { using (StreamWriter sw = new StreamWriter(private_key.txt)) { string f = String.Format({0} {1}
 d n); sw.Write(f); //write the values error = 0; } } catch (Exception ex) { Console.WriteLine(ex.Message); } if (error == 0) { try { using (StreamWriter sw = new StreamWriter(public_key.txt)) { string f = String.Format({0} {1}
 e n); sw.Write(f); //write the values out error = 0; } } catch (Exception ex) { Console.WriteLine(ex.Message); error = 1; } } if (error == 0) { Console.Write(
KEY GENERATION SUCCESSFULL

); //if there wasn't an error } else { Console.Write(
ERROR: KEY GENERATION UNSUCCESSFULL

); //if there was an error return 1; } return 0; } // add facsimile for C rand() function private static int rand() { return random.Next(RAND_MAX + 1); } } class Program { static void Main() { KeyGenerator.gen_keys(); } }

Vulpes · Answer

I see you've also started a new thread on this so I'll answer on there so this thread doesn't become too long.

Adesanya Olusegun · Answer

am sorry for disturbing you once again but i need your help to convert the lines of code //cipher function called from either encrypt or decrypt int cipher(unsigned int exponent unsigned int text unsigned int modulus) { unsigned long result; result = 1; //use the square and multiply algorithm to calculate the result while (exponent > 0) { if ((exponent & 1) == 1) // if the least significant bit of exponent is a 1 { result = (result * text) % modulus; // multiply result so far by text and use modulus to keep result small } exponent >>= 1; // shift the exponent right by 1 losing the most significant bit (0110 becomes 011) text = (text * text) % modulus; //square the text and use modulus to keep small } return result; } //encrypt function called from menu.c int encrypt (void) { unsigned int plaintext exponent modulus result; //Open public_key.txt and read out the two values stored in it FILE *fptr; fptr = fopen(public_key.txtr); if (fptr != NULL) //check if file exists { fscanf(fptr%d %d &exponent &modulus); //read the values fflush(fptr); fclose(fptr); //Get plaintext off user it must be less than the modulus do { printf(Enter Plaintext must be a positive number less than the modulus n: %d:
 modulus); scanf(%d&plaintext); } while (plaintext >= modulus); //encrypt the plaintext using the cipher function result = cipher(exponent plaintext modulus); //print out the result for the user printf(Encrypted message is %d
 result); } else //if the file doesn't exist print the error { printf(
ERROR: ENCRYPTION UNSUCCESSFULL

); //if there was an error return(1); } return 0; } //decrypt function called from menu.c int decrypt (void) { unsigned int ciphertext exponent modulus result; //Open private_key.txt and read out the two values stored in it FILE *fptr; fptr = fopen(private_key.txtr); if (fptr != NULL)//check the file exists { fscanf(fptr%d %d &exponent &modulus); //read values fflush(fptr); fclose(fptr); //Get ciphertext of user printf(Enter ciphertext:
); scanf(%d&ciphertext); //decrypt the message result = cipher(exponent ciphertext modulus); //print the result for the user printf(Decrypted message is %d
 result); } else //if the file doesn't exist print the error { printf(
ERROR: DECRYPTION UNSUCCESSFULL

); //if there was an error return(1); } return 0; }

Adesanya Olusegun · Answer

thanks alot for your assistant i really appreciate it.......and it worked too....thanks