jose85 a écrit :
Hello ,
Hello,
I have exported the public key of my cyberflex 32k card
by sending the values of the modulus and the exponent to the pc, i put these
values into 2 arrays of bytes (the card sent a exp which size is 3 bytes and
a mod of 128 bytes)
i have converted the bytes arrays of the "exp" and the "mod" into Biginteger
like it suggerated in the java doc
but the the message encrypted is different all the time whereas the modulus
and the exponent received from the card are all time the same,
The ciphertext SHALL be different for each RSA Public Key encryption
since you're using a PKCS#1 type 2 padding.
The goal of that padding is a) to make plaintext as wide as the key
(so 1024 bits here) and b) to insert random text to avoid some attacks.
The padding does consist in the following byte stream:
00 02 <random bytes> 00 <text to wrap>
so your results are normal.
here is the snippet of the code that make problem:
BigInteger Exp = new BigInteger(1, exp);
BigInteger Mod = new BigInteger(1, mod);
RSAPublicKeySpec pubKeySpec;
KeyFactory keyFactory;
PublicKey pubKey;
try {
Cipher cipher =Cipher.getInstance("RSA/ECB/PKCS1Padding");
is "ECB" expected here ??
'ECB', 'CBC', ... are relevant for blocks cipher engine only
(meaning mainly symmetric keys based engine).
RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(Mod,Exp);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PublicKey pubKey = keyFactory.generatePublic(pubKeySpec);
cipher.init(Cipher.ENCRYPT_MODE,pubKey);
byte[] env={0x01,0x02,0x03,0x04};
byte[] encrypted = cipher.doFinal(env);
apparently so far, so good.
so of course when i send this encrypted array to the card she isn't able to
decrypt it : --------> erreur 6F00
("of course" ??)
a "good" card application shall never return 6F00 which means
unhandled exception, this is the first evidence that the applet
code is not clean and possibly buggy.
note that the encryption an decryption work well in the card , but not if i
crypt on the pc
for which algo ? does the card also use RSA-PKCS#1 or the (poor)
RSA-X509 (no padding) mode ?
what is the format of the ciphertext returned by the card ?
is it simply 128 bytes or does some extra padding inserted ?
it's a java problem
I don't think so; more likely a JavaCard problem.
One possible issue is cryptography of course but there are also
dozens of possible errors with sequence error, data field format
& content from the card side; you should try more computation
with the card (it is able to encrypt (wrap) and decrypt (unwrap)
with different mechanisms - basically you can wrap in PKCS1 then
unwrap in X509 to check data padding by the card, also you can
encrypt (in raw X509 or PKCS#1, type 1) with card private key
and decrypt in PC with the public key (in RAW mode) to verify
card exponentiation and optional padding.
once you are sure which operation are supported by the card
and which formats it except you will have no trouble to use it
together with PC Java code.
Sylvain.
_______________________________________________
Muscle mailing list
[email protected]
http://lists.drizzle.com/mailman/listinfo/muscle
