Encryption

To securely encrypt a value like a string or integer, you can use symmetric or asymmetric encryption. To encrypt data with a symmetric-key algorithm, you can use the Advanced Encryption Standard (AES). In the next example, we create a new instance of the Aes class and use it to generate a new key and initialization vector (IV). We use the AES to encrypt any type of managed stream. The stream is then wrapped with CryptoStream.

C#

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Aes aes = Aes.Create();
CryptoStream cryptStream = new CryptoStream(fileStream,
aes.CreateEncryptor(aes.Key, aes.VI),
CryptoStreamMode. Write);
Hashing
Hashing is a one-way operation. When you’re using a hashing function to hash nonunique inputs such as passwords, use a salt value added to the original value before hashing.

C#

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public static byte[] HashPassword256(string password)
{
System.Security.Cryptography.SHA256 mySHA256 = System.Security.Cryptography.SHA256.Create();
var encoding = new System.Text.UnicodeEncoding();
return mySHA256.ComputeHash(encoding.GetBytes(password));
}
Random numbers
Temporary password or access codes are intended to be unique per user. You can achieve this uniqueness by introducing random-character generation, and it’s worth noting how the randomness is achieved. You might be familiar with the System.Random class. System.Random is a deterministic pseudo-random sequence generator. It’s predictable and seeded only from the system clock, which means it’s guessable. As a matter of fact, Microsoft Learn documentation explicitly states that you shouldn’t use it for generating passwords. To generate a cryptographically secure random number that’s suitable for creating a random password, you should use a RandomNumberGenerator instance.

C#

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var randomNumberGenerator = System.Security.Cryptography.RandomNumberGenerator.Create();
By using RandomNumberGenerator, you can eliminate the chances of two or more users ending up with the same token or password when they must be unique.

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