Length of the decryption(RSA) string is changing

Question

I have a String which is encrypted with RSA algorithm, When i was trying to decrypt it's working fine.The decryption output will be in byte[].

My question is when i trying to convert the byte[] to a new String(decrypted String) it's getting different length .

If i try with a random string the length is remains same.But if i decrypt the generated aesKey(AES) the length of the byte[] is changing while conversion of new String(decrypted String).

Why i am getting different length incase of aesKey decryption??? Is there any difference between "random string" and "generated aeskey"

String == "t8xypyI6gKlKTkt4Qec7FCor4EpukZXqYQcIDm6YvbtRB9+YBrX0CqyoHOHN91T8RBQS/JD2osbf4ao9Y"SgNbzhfDa2NpJKMEIBWH4TNlF4Ngb8yWdSm3hz3l8FdeFUIy3pyCxkLjU8n4VAxsmgoIQbgd7DJuPiSMZBA9/IVlcCfo/tZjMtSkezITtoT5aVvLxLaTsp08UREdalvXxb5USKi3cAEdqR9TmLJxB004IMv5Eiuvdmcc3fJzO6mnwiHPuGKArd9LjjiqbPQ75uc8NDOFrvleLc5KwSuThS5Xx7tR1qfoX6qefh6SD7FRk5UzyCEnv+eD+mCQ588Jam1A==";

****The above string is encrypted form of the aesKey(generated by KeyGenerator)

If i decrypt this string by using RSA----

private String decrypt(String text, Key privatekey) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
    byte[] dectyptedText = null;

    Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPPadding");
    cipher.init(Cipher.DECRYPT_MODE, privatekey);
    dectyptedText = cipher.doFinal(Base64.getDecoder().decode(text));
    System.out.println(dectyptedText.length);                  //32
    System.out.println(new String(dectyptedText).length());    //30
    System.out.println(new String(dectyptedText).getBytes().length); //60
    return new String(dectyptedText);

}

above, The length is changing in byte string conversions.

Suppose if i encrypt and decrypt with a normal string the lengths are not changing????why????

Answer 1

Likely, the decryptedText contains funny bytes. The documentation says:

public String(byte[] bytes)

Constructs a new String by decoding the specified array of bytes using the platform's default charset. The length of the new String is a function of the charset, and hence may not be equal to the length of the byte array.

The behavior of this constructor when the given bytes are not valid in the default charset is unspecified. The CharsetDecoder class should be used when more control over the decoding process is required.