Hashing

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MD5

TinyCLR OS supports MD5 hash function.

The following commands will calculate the MD5 hash value of a byte array:

Tip

Needed NuGets: GHIElectronics.TinyCLR.Core and GHIElectronics.TinyCLR.Cryptography

var md5 = GHIElectronics.TinyCLR.Cryptography.MD5.Create();
var hashValue = md5.ComputeHash(data); //data is a byte array.

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CRC16

TinyCLR OS supports CRC16.

ComputeHash(byte[] data, int offset, int count);

Large amounts of data can be calculated in chunks and the hash is concatenated automatically. Calling Reset resets the seed value.

var crc16 = new Crc16();
var data = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };

// Uses entire array to build the hash
crc16.Reset(); // reset seed = 0;
var crcVal1 = crc16.ComputeHash(data, 0, data.Length);

// Uses chunks of the array to build the hash
crc16.Reset(); // reset seed = 0;
var crcSeed1 = crc16.ComputeHash(data, 0, 3);
var crcSeed2 = crc16.ComputeHash(data, 3, 1);         
var crcVal2 = crc16.ComputeHash(data, 4, 4); 

// `crcVal1` and `crcVal2` will match.

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SHA1

SHA-1 is most often used to verify that a file has been unaltered. This is done by producing a checksum before the file has been transmitted, and then again once it reaches its destination.

var data = new byte[] { 1, 2, 3, 4, 5 };
var sha1 = SHA1.Create();

var result = sha1.ComputeHash(data);

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HMAC-SHA1

HMACSHA1 is a type of keyed hash algorithm that is constructed from the SHA1 hash function and used as an HMAC, or hash-based message authentication code.

var data = new byte[] { 1, 2, 3, 4, 5 };
var hmacSha1 = new HMACSHA1();

var result = hmacSha1.ComputeHash(data);

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HMAC-SHA256

HMAC-SHA256 offers better security than standard SHA256. It is also required for SAS(Shared Access Signature), needed for Microsoft Azure.

var key = new byte[] { 1, 2, 3, 4, 5, 6 };
var hmacSha256 = new HMACSHA256(key);

var message = "this is for test";
var result = hmacSha256.ComputeHash(System.Text.UTF8Encoding.UTF8.GetBytes(message));