aes - How to make Rijndael CBC mode work in vb.net -

i'm trying make rijndael work in cbc mode. i'm not sure how should it. think problem in current code stream initialized every time in beginning of encryption, no avalanche effect occurs (same data encrypted twice , output of 2 encryption same should not be).

i tried initialize cryptostream once coded crashed because canwrite property of cryptostream goes false after first write cryptostream.

here code have now:

 sub main()          dim rij new rijndaelmanaged         dim iv(15) byte         dim key(15) byte         dim secret() byte = {59, 60, 61}          dim cs icryptotransform         dim cstream cryptostream          dim out() byte         dim newrandom new rngcryptoserviceprovider()          newrandom.getbytes(iv)         newrandom.getbytes(key)          rij = new rijndaelmanaged()          rij.keysize = 128         rij.padding = paddingmode.pkcs7          rij.mode = ciphermode.cbc          rij.iv = iv         rij.key = key         cs = rij.createencryptor()          dim ms_in new memorystream         cstream = new cryptostream(ms_in, cs, cryptostreammode.write)           using cstream             cstream.write(secret, 0, 3)         end using          out = ms_in.toarray         console.writeline(arraytostring(out, out.length))         erase out          ms_in = new memorystream         cstream = new cryptostream(ms_in, cs, cryptostreammode.write)           using cstream             cstream.write(secret, 0, 3)         end using          out = ms_in.toarray         console.writeline(arraytostring(out, out.length))      end sub  

and conversion function convert array string

  public function arraytostring(byval bytes() byte, byval length integer) string          if bytes.length = 0 return string.empty         dim sb new system.text.stringbuilder(length)          dim k integer = length - 1         dim integer          = 0 k             sb.append(chr(bytes(i)))         next           return sb.tostring()      end function 

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this need:

    cs = rij.createencryptor()     dim ms_in new memorystream     cstream = new cryptostream(ms_in, cs, cryptostreammode.write)      using cstream         cstream.write(secret, 0, 3) 'encrypt     end using      out = ms_in.toarray     console.writeline(arraytostring(out, out.length)) 'see encrypted message     erase out      using cstream         cstream.write(secret, 0, 3) 'encrypt, crash here , problem i'm trying solve     end using      out = ms_in.toarray     console.writeline(arraytostring(out, out.length)) 'see encrypted message should not same first 1 

try this:

public sub run()     dim key() byte = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}      dim plaintext1 byte() = {59, 60, 61}      dim plaintext2 byte() = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15, _                              0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15, _                              0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15, _                              0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 _                              }      roundtrip(plaintext1, key)     system.console.writeline()     roundtrip(plaintext2, key)  end sub   public sub roundtrip(byref plaintext byte(), byref key byte())      dim rij new rijndaelmanaged     dim iv(15) byte      dim encryptor icryptotransform     dim decryptor icryptotransform      dim out() byte      'dim newrandom new rngcryptoserviceprovider()     'newrandom.getbytes(iv)     'newrandom.getbytes(key)      console.writeline("original:")     console.writeline(arraytostring(plaintext))     system.console.writeline()      rij = new rijndaelmanaged()     rij.keysize = key.length * 8  ' 16 byte key == 128 bits     rij.padding = paddingmode.pkcs7     rij.mode = ciphermode.cbc     rij.iv = iv     rij.key = key     encryptor = rij.createencryptor()      using msin = new memorystream          using cstream = new cryptostream(msin, encryptor, cryptostreammode.write)             cstream.write(plaintext, 0, plaintext.length)         end using          out = msin.toarray         console.writeline("encrypted:")         console.writeline("{0}", arraytostring(out))         system.console.writeline()      end using      decryptor = rij.createdecryptor()     using msin = new memorystream          using cstream = new cryptostream(msin, decryptor, cryptostreammode.write)             cstream.write(out, 0, out.length)         end using          out = msin.toarray         console.writeline("decrypted:  ")         console.writeline("{0}", arraytostring(out))         system.console.writeline()      end using  end sub   public shared function arraytostring(byval bytes byte()) string      dim sb new system.text.stringbuilder()      dim integer     = 0 bytes.length-1         if (i <> 0 , mod 16 = 0)             sb.append(environment.newline)         end if         sb.append(system.string.format("{0:x2} ", bytes(i)))     next      return sb.tostring().trim()  end function 

i made these basic changes work:

• create decryptor
• properly manage buffers , streams (see using clauses added)

i re-organized little, , modified code use constant iv (all zeros) , use constant key. can repeatable results 1 run next. in real app use randomized iv , use password-derived key. (see rfc2898derivebytes)

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ok, allows code compile. think want see effect of chaining. not easy, maybe show want see:

        integer = 1 2             using ms = new memorystream                 using cstream = new cryptostream(ms, encryptor, cryptostreammode.write)                     j integer = 1                         cstream.write(plaintext, 0, plaintext.length)                     next j                 end using                 out = ms.toarray                 console.writeline("encrypted (cycle {0}):", i)                 console.writeline("{0}", arraytostring(out))                 system.console.writeline()              end using         next