PHP Encrypt/Decrypt whith asymetrics keys

[Benoît]

Hi,
I have generated two keys :
"C:>openssl req -nodes -new -x509 -keyout ben.key -out ben.crt -days
3650"
I try to encrypt/decrypt a string like "JOHN" with these asymetrics
keys. With the following code, it works.
I encrypt with the public key which is in the certificate.
I decrypt with the private key.
But why, the crypted message is different every time I start the
programm...?
_______________ _______________ _______________ ____________
<?php
echo "---CRYPT---<BR>";
$source="JOHN";
echo "Message : $source<BR>";
$fp=fopen("./ben.crt","r");
$pub_key=fread ($fp,8192);
fclose($fp);
//echo $pub_key;
openssl_get_pub lickey($pub_key );
openssl_public_ encrypt ($source,$sourc ecrypt,$pub_key );
echo "Crypted message : ".$sourcecrypt. "<BR><BR>";
$source="";


echo "---DECRYPT---<BR>";
echo "Crypted message : ".$sourcecrypt. "<BR>";
$fp=fopen("./ben.key","r");
$priv_key=fread ($fp,8192);
fclose($fp);
$res=openssl_ge t_privatekey($p riv_key);
openssl_private _decrypt ($sourcecrypt,$ newsource,$res) ;
echo "Source decryptée : $newsource<BR>< BR>";
?>
_______________ _______________ _______________ ______________

Now here is my second question :
In fact I encrypt with a java programm where is my certificate and I
decrypt with a PHP programm like I've just explane before.

_______________ _______________ _______________ ______________
public String crypt(String message) {

//Cert is in LDAP
Certificate cert =
userProvider.ge tUserCertificat e(getCurrentUse rname());

PublicKey publicKey = cert.getPublicK ey();

try{
Provider secProvider = Security.getPro vider("BC");
if (secProvider == null) {
secProvider = new BouncyCastlePro vider();
Security.addPro vider(secProvid er);
}
Cipher encryptCipher = Cipher.getInsta nce("RSA", secProvider);
encryptCipher.i nit(Cipher.ENCR YPT_MODE, publicKey);

//Crypt...
String resultCrypt = new String();
byte[] messageBytes = message.getByte s();
byte[] resultCryptByte s = encryptCipher.d oFinal(messageB ytes);
resultCrypt = arr2str(resultC ryptBytes);

return resultCrypt ;

}catch(Exceptio n e){
//throw ...
}
}
_______________ _______________ _______________ _______________ ____

Why my programm PHP can't decrypt the message? I use evidently the
correct private key which corresponds with the public key.

Thanks for your answers...

[Colin McKinnon]

Re: PHP Encrypt/Decrypt whith asymetrics keys

Benoît wrote:
[color=blue]
> Hi,
> I have generated two keys :
> "C:>openssl req -nodes -new -x509 -keyout ben.key -out ben.crt -days
> 3650"
> I try to encrypt/decrypt a string like "JOHN" with these asymetrics
> keys. With the following code, it works.
> I encrypt with the public key which is in the certificate.
> I decrypt with the private key.
> But why, the crypted message is different every time I start the
> programm...?[/color]

Sounds like a good thing, particularly with short strings - the system is
applying some reversible modification of the data before encoding to
specifically avoid repetition, e.g. instead of:

$encrypted=encr ypt($data, $private_key);

the system is might be doing something like:

$modifier=rand( 0,10000) . time();
$data=base64_en code($data) . ":" . base64_encode($ modifier);
$encrypted=encr ypt($data);

(actually even I could come up with something better if I spent some time
thinking about it - no doubt the openssl people did already).
....so the data is always recoverable but the encrypted message contains
random junk which is discarded.
[color=blue]
>
> Now here is my second question :
> In fact I encrypt with a java programm where is my certificate and I
> decrypt with a PHP programm like I've just explane before.
>[/color]

<snip>
In addition to the reason cited above, openSSL may do all sorts of strange
things to package up the encrypted data.

I would suggest that you start by meking sure you can implement compatable
encryption frm the command line using openSSL.exe (which I suspect will be
straightforward ), then try to reproduce the behaviour in Java (I'm sure the
Java newsgroups can better advise you on your Java code).

HTH

C.