Hashing a string with Sha256

Question

I try to hash a string using SHA256  I m using the following code   using System  using System Security Cryptography  using System Text   public class Hash           public static string getHashSha256 string text                byte   bytes   Encoding Unicode GetBytes text           SHA256Managed hashstring   new SHA256Managed            byte   hash   hashstring ComputeHash bytes           string hashString   string Empty          foreach  byte x in hash                        hashString    String Format   0 x2    x                     return hashString            However  this code gives significantly different results compared to my friends php  as well as online generators  such as This generator   Does anyone know what the error is  Different bases

User · Answer

In the PHP version you can send  true  in the last parameter  but the default is  false   The following algorithm is equivalent to the default PHP s hash function when passing  sha256  as the first parameter   public static string GetSha256FromString string strData                var message   Encoding ASCII GetBytes strData           SHA256Managed hashString   new SHA256Managed            string hex                var hashValue   hashString ComputeHash message           foreach  byte x in hashValue                        hex    String Format   0 x2    x                     return hex

User · Answer

This work for me in  NET Core 3 1  But not in  NET 5 preview 7  using System  using System Security Cryptography  using System Text   namespace PortalAplicaciones Shared Models       public class Encriptar               public static string EncriptaPassWord string Password                        try                               SHA256Managed hasher   new SHA256Managed                     byte   pwdBytes   new UTF8Encoding   GetBytes Password                   byte   keyBytes   hasher ComputeHash pwdBytes                    hasher Dispose                    return Convert ToBase64String keyBytes                             catch  Exception ex                                throw new Exception ex Message  ex

User · Answer

public string EncryptPassword string password  string saltorusername                        using  var sha256   SHA256 Create                                  var saltedPassword   string Format   0  1    salt  password                   byte   saltedPasswordAsBytes   Encoding UTF8 GetBytes saltedPassword                   return Convert ToBase64String sha256 ComputeHash saltedPasswordAsBytes

User · Answer

public static string ComputeSHA256Hash string text        using  var sha256   new SHA256Managed                  return BitConverter ToString sha256 ComputeHash Encoding UTF8 GetBytes text    Replace  -                                  The reason why you get different results is because you don t use the same string encoding  The link you put for the on-line web site that computes SHA256 uses UTF8 Encoding  while in your example you used Unicode Encoding  They are two different encodings  so you don t get the same result  With the example above you get the same SHA256 hash of the linked web site  You need to use the same encoding also in PHP   The Absolute Minimum Every Software Developer Absolutely  Positively Must Know About Unicode and Character Sets  No Excuses    https   www joelonsoftware com 2003 10 08 the-absolute-minimum-every-software-developer-absolutely-positively-must-know-about-unicode-and-character-sets-no-excuses

User · Answer

The shortest and fastest way ever  Only 1 line   public static string StringSha256Hash string text    gt      string IsNullOrEmpty text    string Empty   BitConverter ToString new System Security Cryptography SHA256Managed   ComputeHash System Text Encoding UTF8 GetBytes text    Replace  -   string Empty

User · Answer

I also had this problem with another style of implementation but I forgot where I got it since it was 2 years ago   static string sha256 string randomString        var crypt   new SHA256Managed        string hash   String Empty      byte   crypto   crypt ComputeHash Encoding ASCII GetBytes randomString        foreach  byte theByte in crypto                hash    theByte ToString  x2              return hash      When I input something like abcdefghi2013 for some reason it gives different results and results in errors in my login module  Then I tried modifying the code the same way as suggested by Quuxplusone and changed the encoding from ASCII to UTF8 then it finally worked   static string sha256 string randomString        var crypt   new System Security Cryptography SHA256Managed        var hash   new System Text StringBuilder        byte   crypto   crypt ComputeHash Encoding UTF8 GetBytes randomString        foreach  byte theByte in crypto                hash Append theByte ToString  x2               return hash ToString        Thanks again Quuxplusone for the wonderful and detailed answer

User · Answer

Encoding Unicode is Microsoft s misleading name for UTF-16  a double-wide encoding  used in the Windows world for historical reasons but not used by anyone else   http   msdn microsoft com en-us library system text encoding unicode aspx  If you inspect your bytes array  you ll see that every second byte is 0x00  because of the double-wide encoding    You should be using Encoding UTF8 GetBytes instead   But also  you will see different results depending on whether or not you consider the terminating   0  byte to be part of the data you re hashing  Hashing the two bytes  Hi  will give a different result from hashing the three bytes  Hi   You ll have to decide which you want to do   Presumably you want to do whichever one your friend s PHP code is doing    For ASCII text  Encoding UTF8 will definitely be suitable  If you re aiming for perfect compatibility with your friend s code  even on non-ASCII inputs  you d better try a few test cases with non-ASCII characters such as    and   and see whether your results still match up  If not  you ll have to figure out what encoding your friend is really using  it might be one of the 8-bit  code pages  that used to be popular before the invention of Unicode   Again  I think Windows is the main reason that anyone still needs to worry about  code pages

[c#] Hashing a string with Sha256

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