yakivmospan
commented
7 years ago First of all you need to convert AES key into a string, so later you will be able to encrypt it with RSA. http://stackoverflow.com/questions/5355466/converting-secret-key-into-a-string-and-vice-versa
SecretKey secretKey;
String stringKey;
try {secretKey = KeyGenerator.getInstance("AES").generateKey();}
catch (NoSuchAlgorithmException e) {/* LOG YOUR EXCEPTION */}
if (secretKey != null) {stringKey = Base64.encodeToString(secretKey.getEncoded(), Base64.DEFAULT)}If your public RSA key is inside of apk (in assets maybe) you will need to read it like this - http://stackoverflow.com/questions/11410770/load-rsa-public-key-from-file.
Then you can use that RSA key to encrypt a AES key text with Crypto#String encrypt(@NonNull String data, @NonNull Key key, boolean useInitialisationVectors).
// create a string from AES Secret Key
String aesKey;
// read Public Key from file
PublicKey publicKey;
//Encrypt AES key with public RSA key
Crypto crypto = new Crypto(TRANSFORMATION_ASYMMETRIC);
String encryptedAESKey = crypto.encrypt(aesKey, publicKey, false);Unfortunately in current versionCrypto has no function to encrypt/decrypt whole file, instead you can open a file, read it line by line, encrypt each line, and save encrypted line to another file.
CtrlShiftTab
Not so much an issue as a feature query, hope this is ok. Would it be possible to perform multiparty encryption/decryption i.e. encrypt a file with AES shared key and encrypt this key with multiple public RSA keys?
Like in openssl, please find example below.
openssl smime -encrypt -aes256 -in secrets.txt -out secrets.txt.enc -outform PEM bob.pub alice.pub frank.pub carol.pub
The recipients could just use their private keys to decrypt like maybe:
openssl smime -decrypt -in secrets.txt.enc -inform PEM -inkey alice.key
Any hints very much appreciated! thanks