Base64 String throwing invalid character error

Question

I keep getting a Base64 invalid character error even though I shouldn t   The program takes an XML file and exports it to a document  If the user wants  it will compress the file as well  The compression works fine and returns a Base64 String which is encoded into UTF-8 and written to a file   When its time to reload the document into the program I have to check whether its compressed or not  the code is simply   byte   gzBuffer   System Convert FromBase64String text   return  1F-8B-08     BitConverter ToString new List lt Byte gt  gzBuffer  GetRange 4  3  ToArray       It checks the beginning of the string to see if it has GZips code in it   Now the thing is  all my tests work  I take a string  compress it  decompress it  and compare it to the original  The problem is when I get the string returned from an ADO Recordset  The string is exactly what was written to the file  with the addition of a   0  at the end  but I don t think that even does anything  even trimmed off it still throws   I even copy and pasted the entire string into a test method and compress decompress that  Works fine   The tests will pass but the code will fail using the exact same string  The only difference is instead of just declaring a regular string and passing it in I m getting one returned from a recordset   Any ideas on what am I doing wrong

User · Answer

Whether null char is allowed or not really depends on base64 codec in question. Given vagueness of Base64 standard (there is no authoritative exact specification), many implementations would just ignore it as white space. And then others can flag it as a problem. And buggiest ones wouldn't notice and would happily try decoding it... :-/

But it sounds c# implementation does not like it (which is one valid approach) so if removing it helps, that should be done.

One minor additional comment: UTF-8 is not a requirement, ISO-8859-x aka Latin-x, and 7-bit Ascii would work as well. This because Base64 was specifically designed to only use 7-bit subset which works with all 7-bit ascii compatible encodings.

User · Answer

string stringToDecrypt   HttpContext Current Request QueryString ToString       change to  string stringToDecrypt   HttpUtility UrlDecode HttpContext Current Request QueryString ToString

User · Answer

You say     The string is exactly what was written   to the file  with the addition of a     0  at the end  but I don t think   that even does anything     In fact  it does do something  it causes your code to throw a FormatException  Invalid character in a Base-64 string   because the Convert FromBase64String does not consider   0  to be a valid Base64 character     byte   data1   Convert FromBase64String  AAAA 0       Throws exception   byte   data2   Convert FromBase64String  AAAA         Works   Solution  Get rid of the zero termination    Maybe call  Trim   0     Notes   The MSDN docs for Convert FromBase64String say it will throw a FormatException when     The length of s  ignoring white space   characters  is not zero or a multiple   of 4       -or-       The format of s is invalid  s contains a non-base 64 character  more   than two padding characters  or a   non-white space character among the   padding characters    and that     The base 64 digits in ascending order   from zero are the uppercase characters    A  to  Z   lowercase characters  a    to  z   numerals  0  to  9   and the   symbols     and

User · Answer

If removing  0 from the end of string is impossible  you can add your own character for each string you encode  and remove it on decode

User · Answer

One gotcha to do with converting Base64 from a string is that some conversion functions use the preceding  data image jpg base64   and others only accept the actual data

[c#] Base64 String throwing invalid character error

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