That sounds risky. You're using a cryptographic primitive in a non-standard way, and in danger of having created a weakness. For example, are you sure that you

That sounds risky. You're using a cryptographic primitive in a non-standard way, and in danger of having created a weakness. For example, are you sure that your cipher doesn't have the property that for any text.Encrypt(key1).Encrypt(key2) there's an equivalent text.Encrypt(key3)? Some ciphers have that property (e.g. the one time pad). That would reduce your security from 10^N to... 10.