encryption - vb.net AES decryption returns "data is incomplete block" -

i'm aware of other thread on issue (aes decryption error " input data not complete block." error vb.net), i'm either not implementing solutions offered there correctly, or particular variant of issue isn't covered solutions. in event i'm getting incomplete block error following code

private gd system.security.cryptography.aes = system.security.cryptography.aes.create private pdb new system.security.cryptography.rfc2898derivebytes(ek, new byte() {&h49, &h76, &h61, &h6e, &h20, &h4d, &h65, &h64, &h76, &h65, &h64, &h65, &h76})  public function decrypt(byval val string) string     dim ret string = nothing     dim ttb new system.text.utf8encoding      try         dim input() byte = ttb.getbytes(val)          using ms new system.io.memorystream(input)             using cs new system.security.cryptography.cryptostream(ms, gd.createdecryptor(pdb.getbytes(32), pdb.getbytes(16)), security.cryptography.cryptostreammode.read)                 using sr new system.io.streamreader(cs)                     ret = sr.readtoend()                 end using             end using         end using          input = nothing     catch ex exception         el.adderr("encountered error while decrypting provided text " & fname & ". error details: " & ex.message, path)     end try      return ret end function 

ek key, i'll not including. it's string though, nothing special.

i've tried several other methods decrypt based on guidance on msdn site, dreamincode, etc. none worked, had different issues (typically returning blank string). seeing version of code closely mirrors encryption code, i'd stick (or @ least close can while still having functional code).

despite comments, still lack understanding of intentions. therefore, sample code below may not provide want, @ least should give idea how employ cryptographic functions. particularly, notable difference approach encryption key , initialization vector computed once , messages, rather reevaluated on each occasion, because latter prone synchronization errors — such when reuse single crypto object communicate multiple parties, or when messages lost in transmission.

public shared sub test()      ' note: should not hard-code sensitive information in source files, ever!     dim skeypreimage string = "mysuperpassword"     dim omycrypto new mycrypto(skeypreimage)      dim splaintext string = "my super secret data"     dim sencrypted string = omycrypto.encrypttext(splaintext)     dim sdecrypted string = omycrypto.decrypttext(sencrypted)      console.out.writeline("plaintext: {0}", splaintext) ' "my super secret data"     console.out.writeline("encrypted: {0}", sencrypted) ' "72062997872dc4b4d1bcbf48d5d30df0d498b20630cafa28d584ccc3030fc5f1"     console.out.writeline("decrypted: {0}", sdecrypted) ' "my super secret data"  end sub  public class mycrypto      private shared textencoding text.encoding = text.encoding.utf8      private cipherengine system.security.cryptography.symmetricalgorithm      ' note: unlike in question, same key , iv reused messages.     private cipherkey() byte     private cipheriv() byte      public sub new(byval skeypreimage string)          dim abkeypreimage() byte = textencoding.getbytes(skeypreimage)         dim abkeysalt() byte = textencoding.getbytes("ivan medvedev")          const keyderivationrounds integer = 1 << 12         dim okeyderivationengine new system.security.cryptography.rfc2898derivebytes(abkeypreimage, abkeysalt, keyderivationrounds)          me.cipherengine = system.security.cryptography.aes.create()         me.cipherengine.padding = security.cryptography.paddingmode.pkcs7         me.cipherkey = okeyderivationengine.getbytes(me.cipherengine.keysize >> 3)         me.cipheriv = okeyderivationengine.getbytes(me.cipherengine.blocksize >> 3)      end sub      public function encrypt(byval abplaintext() byte) byte()          dim abciphertext() byte          using hstreamsource new system.io.memorystream(abplaintext),                 hstreamcipher new system.security.cryptography.cryptostream(                     hstreamsource,                     me.cipherengine.createencryptor(me.cipherkey, me.cipheriv),                     security.cryptography.cryptostreammode.read),                 hstreamtarget new system.io.memorystream              hstreamcipher.copyto(hstreamtarget)             abciphertext = hstreamtarget.toarray()          end using          return abciphertext     end function      public function decrypt(byval abciphertext() byte) byte()          dim abplaintext() byte          using hstreamsource new system.io.memorystream(abciphertext),                 hstreamcipher new system.security.cryptography.cryptostream(                     hstreamsource,                     me.cipherengine.createdecryptor(me.cipherkey, me.cipheriv),                     security.cryptography.cryptostreammode.read),                 hstreamtarget new system.io.memorystream              hstreamcipher.copyto(hstreamtarget)             abplaintext = hstreamtarget.toarray()          end using          return abplaintext     end function      public function encrypttext(byval splaintext string) string         dim abplaintext() byte = textencoding.getbytes(splaintext)         dim abciphertext() byte = me.encrypt(abplaintext)         dim sciphertext string = hex.format(abciphertext)         return sciphertext     end function      public function decrypttext(byval sciphertext string) string         dim abciphertext() byte = hex.parse(sciphertext)         dim abplaintext() byte = me.decrypt(abciphertext)         dim splaintext string = textencoding.getchars(abplaintext)         return splaintext     end function  end class  public class hex      public shared function format(byval abvalue() byte) string         dim aschars(0 abvalue.length * 2 - 1) char         dim ndxchar integer = 0         ndxbyte integer = 0 abvalue.length - 1             dim bnibblehi byte = abvalue(ndxbyte) >> 4, bnibblelo byte = cbyte(abvalue(ndxbyte) , &hfus)             aschars(ndxchar) = convert.tochar(if(bnibblehi <= 9, &h30us + bnibblehi, &h37us + bnibblehi)) : ndxchar += 1             aschars(ndxchar) = convert.tochar(if(bnibblelo <= 9, &h30us + bnibblelo, &h37us + bnibblelo)) : ndxchar += 1         next         return new string(aschars)     end function      public shared function parse(byval svalue string) byte()          if string.isnullorempty(svalue) return new byte() {}         if (svalue.length mod 2) > 0 return nothing          dim ndxtext integer = 0         dim ndxbytemax integer = (svalue.length \ 2) - 1         dim abvalue(0 ndxbytemax) byte          try             ndxbyte integer = 0 ndxbytemax                 abvalue(ndxbyte) = convert.tobyte(svalue.substring(ndxtext, 2), 16)                 ndxtext += 2             next         catch ex exception             return nothing         end try          return abvalue     end function  end class 

again, please, note example. not endorsing kind of protection techniques shown here, because task remains unknown. code above illustrates syntax , semantics — not how right.