Send RSA Public Key in Java to PHP server - php

Question

I'm having trouble trying to convert a Java generated RSA Public KEY to string format so I can use it on the PHP side. I tried converting it to string but the encryption fails on the PHP side. I generate a public Key in Java like this:
KeyPairGenerator k = KeyPairGenerator.getInstance("RSA");
k.initialize(1024);
KeyPair kp = k.genKeyPair();
PublicKey publicKey = kp.getPublic();
PrivateKey privateKey = kp.getPrivate();
and the PublicKey when outputted to String looks something like this:
RSA Public Key
modulus: eded852d98899fd083b6b989cbdbb41c0cf604ccdc3c4b46a6e3bdf92be898db1c53133dba4fcbc3bd7e8934b7b212856146169858ef2177e9c04c995d4fb61f9957eb6ff61a1183de03e5459ecbae7d1196778be844127fd7e80668b57037cab7a3e56c02cb881c3fb2aaddd47e5cae49c14582be01722cfa5352d9bdc97a37
public exponent: 10001
I then encode this PublicKey like this:
byte[] pKbytes = Base64.encode(publicKey.getEncoded(), 0);
String pK = new String(pKbytes);
String pubKey = "-----BEGIN PUBLIC KEY-----\n" + pK + "-----END PUBLIC KEY-----\n";
and that outputted looks something like this:
-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDt7YUtmImf0
IO2uYnL27QcDPYEzNw8S0am4735
K+iY2xxTEz26T8vDvX6JNLeyEoVhRhaYWO8hd+nATJldT7Yf
mVfrb/YaEYPeA+VFnsuufRGWd4vo
RBJ/1+gGaLVwN8q3o+VsAsuIHD+yqt3UflyuScFFgr4Bciz
6U1LZvcl6NwIDAQAB
-----END PUBLIC KEY-----
which looks similar to the format I have on the PHP side. Encoding it using Base64 gives the final format I intend for the key String.
LS0tLS1CRUdJTiBQVUJMSUMgS0VZLS0tLS1NSUdmTUEwR0NTcUdTSWIzRFFFQkFRVUFBNEdOQURD
QmlRS0JnUUR0N1lVdG1JbWYwSU8ydVluTDI3UWNEUFlFek53OFMwYW00NzM1SytpWTJ4eFRFejI2
VDh2RHZYNkpOTGV5RW9WaFJoYVlXTzhoZCtuQVRKbGRUN1lmbVZmcmIvWWFFWVBlQStWRm5zdXVm
UkdXZDR2b1JCSi8xK2dHYUxWd044cTNvK1ZzQXN1SUhEK3lxdDNVZmx5dVNjRkZncjRCY2l6NlUx
TFp2Y2w2TndJREFRQUItLS0tLUVORCBQVUJMSUMgS0VZLS0tLS0=
After all this, the key doesn't seem to work. It encrypts a message with the key I send it but when I send it back to the Java/Android app (which contains the private key) it can't decrypt it. I've been able to do this vice-versa (i.e. take a encoded key string from PHP and convert it to a Public Key to be used by the Java/Android app) Anything I'm doing wrong here? My gut tells me I'm sending the wrong string to the PHP server
Here's what the stack Trace in Java looks like :
03-02 12:02:26.170 W/System.err﹕ java.lang.ArrayIndexOutOfBoundsException: too much data for RSA block
03-02 12:02:26.182 W/System.err﹕ at com.android.org.bouncycastle.jcajce.provider.asymmetric.rsa.CipherSpi.engineDoFinal(CipherSpi.java:464)
03-02 12:02:26.186 W/System.err﹕ at javax.crypto.Cipher.doFinal(Cipher.java:1204)
03-02 12:02:26.186 W/System.err﹕ at com.app.test.NQ.NQCrypto.decrypt(NQCrypto.java:116)
Here is how I attempt to decrypt the data in Java:
public static String decrypt(String data) throws Exception {
Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA-1AndMGF1Padding", "BC");
cipher.init(Cipher.DECRYPT_MODE, privateKey);
// Base 64 encode the encrypted data
byte[] encryptedBytes = Base64.encode(cipher.doFinal(data.getBytes()), 0);
return new String(encryptedBytes);
}

Answer 1

Your decryption code looks wrong:
cipher.doFinal(data.getBytes())
Your data variable is a string, but strings can't hold raw encrypted data without corrupting it. Unless your ciphertext is actually hex-encoded or base64-encoded etc. In which case, getBytes() is not the right way to decode that into a byte array.
So either fix the way you are sending your ciphertext, or correct the way you decode your ciphertext to a byte array.