static String getEncryptedLink(String sLink) {
        Blob cipherText = Crypto.encryptWithManagedIV('AES256', getKey(),
        Blob.valueOf(sLink));
        String encodedCipherText = EncodingUtil.convertToHex(cipherText);
        return EncodingUtil.urlEncode(encodedCipherText,'UTF-8') ;
    }
}

static String getPlainLink(String sEncryptedLink) {
        String sCleanLink = EncodingUtil.urlDecode(sEncryptedLink,'UTF-8');
        Blob encodedEncryptedBlob = EncodingUtil.convertFromHex(sCleanLink);
        Blob decryptedBlob = Crypto.decryptWithManagedIV('AES256', getKey(),
        encodedEncryptedBlob);
        String decryptedClearText = decryptedBlob.toString();
        return decryptedClearText;
}