RSA Encryption: Difference between Java and Android
android, encryption, java, public-key-encryption, rsa
Solution
Im doing RSA Encrypt in Android 2.2+ and decrypt on a tomcat 6 java 1.6 server.
I was getting this exact problem, reading all over the place and in part thanks to @Femi 's answer I came across what I needed.
The solution was to use the folowing algorithm specification for the Cipher:
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
This works doing encryption from both Android and BlackBerry smartphones. I know its been four months since the question was asked, but just in case someone else goes through this problem.
Problem
I am using RSA to encrypt username and password on Android and decrypt them on server (tomcat 6, java 1.6). Android Encryption: ``` PublicKey pubKey = readPublicKeyFromFile(mod, ex); Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.ENCRYPT_MODE, pubKey); byte[] cipherData = cipher.doFinal(data); return cipherData; ``` Java Tomcat Decryption: ``` PrivateKey pubKey = readPrivateKeyFromFile(mod, ex); Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.DECRYPT_MODE, pubKey); byte[] cipherData = cipher.doFinal(data); return cipherData; ``` If I use the android part OUTSIDE android (Just in a main method) it works fine. But not inside my android (Emulator). On de server side I get the following error: ``` javax.crypto.BadPaddingException: Blocktype mismatch: 0 at sun.security.rsa.RSAPadding.unpadV15(RSAPadding.java:311) at sun.security.rsa.RSAPadding.unpad(RSAPadding.java:255) at com.sun.crypto.provider.RSACipher.a(DashoA13*..) at com.sun.crypto.provider.RSACipher.engineDoFinal(DashoA13*..) at javax.crypto.Cipher.doFinal(DashoA13*..) ``` I keep the mod and ex as BigIntegers constants so I don't write them in to a file. I know that there are difference between java1.6 and java 1.5 encryption, so both are compiled with java 1.6. Some debug info: During debug in android I can see that pubKey contains modulus and exponent in hexadecimal. And if I debug in a main method (again the same code) I can see that pubKey contains modulus and exponent in decimal. What am I doing wrong? Thanks