# IDEA (International Data Encryption Algorithm)

I don't know how to perform Multiplication Modulo and Addition Modulo in IDEA (International Data Encryption Algorithm).

• What have you tried so far? – AleksanderRas Dec 5 at 15:48
• Addition is per modular arithmetic modulo $2^{16}$. Multiplication is modulo $2^{16}+1$, except 0x0000 is changed to 0x10000 in arguments, and vice-versa for result. Anything unclear? – fgrieu Dec 5 at 16:01
• What is the result of 2^14*2^12 modulo 2^16+1 step by step – Ali Dec 5 at 22:09
• What is the result of 00000000+10000000 modulo 2^7+1 – Ali Dec 5 at 22:11
• It is probably better to integrate these requests in the question. It would not hurt to extend the question a bit more with the context: that IDEA uses IDEA specific methods to perform these calculations may be lost on most readers, resulting in unfortunate downvotes. We really value any effort that is put in the question (such as trying to calculate the values yourself). – Maarten Bodewes Dec 6 at 15:26