java - AES decryption after sending message to IP address -

so making app sends secure messages specified ip address. using aes encrypt message , part works great. able encrypt message , decrypt before send message. however, when try decrypt message has been recieved server, can not decrypt it. gets displayed in it's encrypted form.

i error "java.lang.numberformatexception: invalid int: "ne"" , think may have character encoding or something? string altered in way when sent on network?

here snippets may related issue.

public static string encrypt(string seed, string cleartext)         throws exception {     byte[] rawkey = getrawkey(seed.getbytes());     byte[] result = encrypt(rawkey, cleartext.getbytes());     return tohex(result); }  public static string decrypt(string seed, string encrypted)         throws exception {     byte[] rawkey = getrawkey(seed.getbytes());     byte[] enc = tobyte(encrypted);     byte[] result = decrypt(rawkey, enc);     return new string(result); }   public static byte[] tobyte(string hexstring) {     int len = hexstring.length() / 2;     byte[] result = new byte[len];     (int = 0; < len; i++)         result[i] = integer.valueof(hexstring.substring(2 * i, 2 * + 2),                 16).bytevalue();     return result; }  public static string tohex(byte[] buf) {     if (buf == null)         return "";     stringbuffer result = new stringbuffer(2 * buf.length);     (int = 0; < buf.length; i++) {         appendhex(result, buf[i]);     }     return result.tostring(); } 

this decryption message displayed.

while (!goout) {     if (datainputstream.available() > 0) {         incoming = datainputstream.readutf();          if(encrypt == true) {             try{                 msglog += aeshelper.decrypt(seed,incoming);             } catch (exception e) {                 e.printstacktrace();             }          } else msglog += incoming;            mainactivity.this.runonuithread(new runnable() {              @override             public void run() {                 chatmsg.settext(msglog);             }         }); 

this encrypting message:

onclicklistener buttonencryptonclicklistener = new onclicklistener()   {         public void onclick(view v) {             if (chatclientthread == null) {                 return;             }             if (edittextsay.gettext().tostring().equals("")) {                 return;             }              if(!edittextsay.gettext().tostring().equals("")){                  string message = edittextsay.gettext().tostring();                 encrypt = true;                 int seclvl = integer.parseint(edittextsecurity.gettext().tostring());                  string encryptedmsg;                 try {                      encryptedmsg = aeshelper.encrypt(seed, message);                     textencryptedmsg.settext(encryptedmsg);                     textencryptedmsg.setvisibility(view.visible);                  } catch (exception e) {                     e.printstacktrace();                  }              }          }     }; 

this sending message:

onclicklistener buttonsendonclicklistener = new onclicklistener() {          @override         public void onclick(view v) {             if (edittextsay.gettext().tostring().equals("")) {                 return;             }              if(chatclientthread==null){                 return;             }              if (encrypt == true){                  chatclientthread.sendmsg(textencryptedmsg.gettext().tostring() + "\n");             } else {                 chatclientthread.sendmsg(edittextsay.gettext().tostring() + "\n");             }              edittextsay.settext("");             textencryptedmsg.settext("");             textdecryptedmsg.settext("");             encrypt = false;             incomingmsg.setvisibility(view.visible);         }      }; 

i'll assume you're sending ciphertext in hex encoded form. datainputstream#readutf() reads single unicode character stream. since you're sending hex characters mean single ciphertext byte can constructed 2 of such unicode characters.

the problem aes operates on blocks. trying decrypt every single "half"-byte separately won't work.

you need rewrite decryption method either

• use streaming decryption or
• read whole ciphertext , decrypt in 1 go.

if want try streaming decryption, have 2 options:

• update internal buffer of cipher object using offset-version of cipher#update() or
• use cipherinputstream.

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here (pseudo-code) example of reading whole thing before trying decrypt it:

stringbuilder incoming = new stringbuilder(); while (!goout && ) {     incoming.append(datainputstream.readutf()); } if(encrypt == true) {     try{         msglog += aeshelper.decrypt(seed, incoming.tostring());     } catch (exception e) {         e.printstacktrace();     } } else msglog += incoming;