Function to encode MD5 in SQL-Server 2012

Hi.

I have created this function to get the MD5 code of a text:

FUNCTION [dbo].[fn_md5] (@data_a_codificar varchar) 
RETURNS CHAR(32) AS
BEGIN
  RETURN convert(varchar,hashbytes('MD5',@data_a_codificar),2)
END

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Then I execute these two sentences:

select dbo.fn_md5('Hello');

select convert(char,hashbytes('MD5','Hello'),2)

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Why aren't they returning the same values?