Migrating users from ASP.NET Identity Core (2.0) to

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False alarm - my PasswordHash data was incorrect from the start. All is good now.

This post has it correct:

“value”: “$pbkdf2-sha1$i=1000,l=32${salt}${hash}”

For anyone else in the future in a similar situation - here’s a quick C# script I wrote that you can run to produce the string you’ll need to put in hash.value in your user import JSON payload:

	public static void Main(string[] args)
	{
		var passwordhash_string_fromdb = "YOUR_PASSWORDHASH_BASE64_STRING";
		var passwordhash_bytes = Convert.FromBase64String(passwordhash_string_fromdb);

		var salt_bytes = new List<byte>();
		var pw_bytes = new List<byte>();
		
		// Break down passwordhash_string_fromdb into bytes representing salt and pw
		// The first byte represents the version of Identity being used (0 == v2.0; 1 == v3.0)
		// This script will not work if your password was not hashed using v2
		// For v2, bytes 1-17 represent the salt and bytes 18-49 represent the password
		// reference: https://github.com/aspnet/AspNetIdentity/blob/main/src/Microsoft.AspNet.Identity.Core/Crypto.cs
		if (passwordhash_bytes[0] != 0)
		{
			Console.WriteLine("This script will not work for you because your password was hashed using something other than Identity v2");
			return;
		}
		for (var i = 0; i < passwordhash_bytes.Length; i++)
		{		
			if (i > 0 && i < 17)
				salt_bytes.Add(passwordhash_bytes[i]);
			else if (i >= 17 && i <= 49)
				pw_bytes.Add(passwordhash_bytes[i]);
		}
		
		// Convert to byte array
		var salt_bytearray = salt_bytes.ToArray();			
		
		// Convert to byte array
		var pw_bytearray = pw_bytes.ToArray();
				
		// Convert both back to base64 and Remove base 64 padding aka '='
		var salt_b64_nopadding = Convert.ToBase64String(salt_bytearray).Replace('=',' ').Trim(' ');
		var pw_b64_nopadding = Convert.ToBase64String(pw_bytearray).Replace('=',' ').Trim(' ');	

		// PHC string format
		var pbkdf2string = ($"$pbkdf2-sha1$i=1000,l=32${salt_b64_nopadding}${pw_b64_nopadding}");

 		// pbkdf2string: copy this to hash.value in your json payload
		Console.WriteLine(pbkdf2string);
	}
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