Here is some code for generating random passwords and checking Password strength based on some criterias in C#
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Cryptography;
public static class RandomPasswordGenerator
{
// Define default min and max password lengths.
private static int DEFAULT_MIN_PASSWORD_LENGTH = 8;
private static int DEFAULT_MAX_PASSWORD_LENGTH = 10;
// Define supported password characters divided into groups.
// You can add (or remove) characters to (from) these groups.
private static string PASSWORD_CHARS_LCASE = "abcdefghijkmnopqrstuvwxyz";
private static string PASSWORD_CHARS_UCASE = "ABCDEFGHJKLMNPQRSTUVWXYZ";
private static string PASSWORD_CHARS_NUMERIC = "23456789";
private static string PASSWORD_CHARS_SPECIAL = "*$-+?_&=!%{}/";
public static string Generate()
{
return Generate(DEFAULT_MIN_PASSWORD_LENGTH,
DEFAULT_MAX_PASSWORD_LENGTH);
}
public static string Generate(int length)
{
return Generate(length, length);
}
public static string Generate(int minLength,
int maxLength)
{
// Make sure that input parameters are valid.
if (minLength <= 0 || maxLength <= 0 || minLength > maxLength)
return null;
// Create a local array containing supported password characters
// grouped by types. You can remove character groups from this
// array, but doing so will weaken the password strength.
char[][] charGroups = new char[][]
{
PASSWORD_CHARS_LCASE.ToCharArray(),
PASSWORD_CHARS_UCASE.ToCharArray(),
PASSWORD_CHARS_NUMERIC.ToCharArray(),
PASSWORD_CHARS_SPECIAL.ToCharArray()
};
// Use this array to track the number of unused characters in each
// character group.
int[] charsLeftInGroup = new int[charGroups.Length];
// Initially, all characters in each group are not used.
for (int i = 0; i < charsLeftInGroup.Length; i++)
charsLeftInGroup[i] = charGroups[i].Length;
// Use this array to track (iterate through) unused character groups.
int[] leftGroupsOrder = new int[charGroups.Length];
// Initially, all character groups are not used.
for (int i = 0; i < leftGroupsOrder.Length; i++)
leftGroupsOrder[i] = i;
// Because we cannot use the default randomizer, which is based on the
// current time (it will produce the same "random" number within a
// second), we will use a random number generator to seed the
// randomizer.
// Use a 4-byte array to fill it with random bytes and convert it then
// to an integer value.
byte[] randomBytes = new byte[4];
// Generate 4 random bytes.
RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
rng.GetBytes(randomBytes);
// Convert 4 bytes into a 32-bit integer value.
int seed = (randomBytes[0] & 0x7f) << 24 |
randomBytes[1] << 16 |
randomBytes[2] << 8 |
randomBytes[3];
// Now, this is real randomization.
Random random = new Random(seed);
// This array will hold password characters.
char[] password = null;
// Allocate appropriate memory for the password.
if (minLength < maxLength)
password = new char[random.Next(minLength, maxLength + 1)];
else
password = new char[minLength];
// Index of the next character to be added to password.
int nextCharIdx;
// Index of the next character group to be processed.
int nextGroupIdx;
// Index which will be used to track not processed character groups.
int nextLeftGroupsOrderIdx;
// Index of the last non-processed character in a group.
int lastCharIdx;
// Index of the last non-processed group.
int lastLeftGroupsOrderIdx = leftGroupsOrder.Length - 1;
// Generate password characters one at a time.
for (int i = 0; i < password.Length; i++)
{
// If only one character group remained unprocessed, process it;
// otherwise, pick a random character group from the unprocessed
// group list. To allow a special character to appear in the
// first position, increment the second parameter of the Next
// function call by one, i.e. lastLeftGroupsOrderIdx + 1.
if (lastLeftGroupsOrderIdx == 0)
nextLeftGroupsOrderIdx = 0;
else
nextLeftGroupsOrderIdx = random.Next(0,
lastLeftGroupsOrderIdx);
// Get the actual index of the character group, from which we will
// pick the next character.
nextGroupIdx = leftGroupsOrder[nextLeftGroupsOrderIdx];
// Get the index of the last unprocessed characters in this group.
lastCharIdx = charsLeftInGroup[nextGroupIdx] - 1;
// If only one unprocessed character is left, pick it; otherwise,
// get a random character from the unused character list.
if (lastCharIdx == 0)
nextCharIdx = 0;
else
nextCharIdx = random.Next(0, lastCharIdx + 1);
// Add this character to the password.
password[i] = charGroups[nextGroupIdx][nextCharIdx];
// If we processed the last character in this group, start over.
if (lastCharIdx == 0)
charsLeftInGroup[nextGroupIdx] =
charGroups[nextGroupIdx].Length;
// There are more unprocessed characters left.
else
{
// Swap processed character with the last unprocessed character
// so that we don't pick it until we process all characters in
// this group.
if (lastCharIdx != nextCharIdx)
{
char temp = charGroups[nextGroupIdx][lastCharIdx];
charGroups[nextGroupIdx][lastCharIdx] =
charGroups[nextGroupIdx][nextCharIdx];
charGroups[nextGroupIdx][nextCharIdx] = temp;
}
// Decrement the number of unprocessed characters in
// this group.
charsLeftInGroup[nextGroupIdx]--;
}
// If we processed the last group, start all over.
if (lastLeftGroupsOrderIdx == 0)
lastLeftGroupsOrderIdx = leftGroupsOrder.Length - 1;
// There are more unprocessed groups left.
else
{
// Swap processed group with the last unprocessed group
// so that we don't pick it until we process all groups.
if (lastLeftGroupsOrderIdx != nextLeftGroupsOrderIdx)
{
int temp = leftGroupsOrder[lastLeftGroupsOrderIdx];
leftGroupsOrder[lastLeftGroupsOrderIdx] =
leftGroupsOrder[nextLeftGroupsOrderIdx];
leftGroupsOrder[nextLeftGroupsOrderIdx] = temp;
}
// Decrement the number of unprocessed groups.
lastLeftGroupsOrderIdx--;
}
}
// Convert password characters into a string and return the result.
return new string(password);
}
// this function actually checking whether the password is strong based on some criterias
public static bool IsPasswordStrong(string passwd)
{
bool isContainsLCase = false;
bool isContainsUCase = false;
bool isContainsNumeric = false;
char[] PASSWORD_CHAR_LCASE = { 'a', 'b', 'c', 'd', 'e', 'f', 'g','h', 'i', 'j', 'k', 'l','m', 'n', 'o', 'p', 'q', 'r', 's', 't','u','v', 'w', 'x', 'y', 'z' };
char[] PASSWORD_CHAR_UCASE = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H','I', 'J', 'K', 'L', 'M', 'N','O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
char[] PASSWORD_CHAR_NUMERIC = {'0','1', '2', '3', '4', '5', '6', '7', '8', '9' };
char[] PASSWORD_CHAR_SPECIAL = "*$-+?_&=!%{}/".ToCharArray();
//checking length
if (passwd.Length < 6)
{
return false;
}
// checking uppercase exists or not you can add or remove the letters you want
foreach (char ch in PASSWORD_CHAR_LCASE)
{
if (passwd.IndexOf(ch) > -1)
{
if (ch == 'l')
{
isContainsLCase = false;
break;
}
else
{
isContainsLCase = true;
}
}
}
if (isContainsLCase == false) // No Lowercase found or invalid letter found so return false
{
return false;
}
// checking uppercase exists or not
foreach (char ch in PASSWORD_CHAR_UCASE)
{
if (passwd.IndexOf(ch) > -1)
{
if (ch == 'I' || ch=='O')
{
isContainsUCase = false;
break;
}
else
{
isContainsUCase = true;
}
}
}
if (isContainsUCase == false) // No Uppercase found or invalid uppercase found so return false
{
return false;
}
// checking numeric value exists or not
foreach (char ch in PASSWORD_CHAR_NUMERIC)
{
if (passwd.IndexOf(ch) > -1)
{
if (ch == '0' || ch == '1')
{
isContainsNumeric = false;
break;
}
else
{
isContainsNumeric = true;
}
}
}
if (isContainsNumeric == false) // No Numeric found or invalid numeric found so return false
{
return false;
}
return true;
}
}
