# Tagged Questions

The International Data Encryption Algorithm (IDEA) is a block cipher developed in 1991 by James Massey and Xuejia Lai.

83 views

### Weak key schedule IDEA [closed]

Why was such a weak key schedule chosen for IDEA? The key schedule of IDEA works like this: Divide the key (128 bit) into 8 round keys, each 16 bit long. This are the first 8 "round" keys (6 keys per ...
221 views

### How is multiplication inverted in IDEA's decryption round?

As we can see in the picture we have a multiplication in this algorithm, we know that two 16 bit inputs should have a 32 bit output, but here we just use 16 bits of the 32 bit output. For ...
312 views

### How do I generate decryption keys for the IDEA algorithm from the 128 bit key?

I am trying to implement IDEA algorithm in C#, just to learn how it works. I have taken a 128 bit binary key and generated the 52 encryption keys using the following code: ...
500 views

### How to perform Multiplicative Inverse Modulo in IDEA

How to perform the Multiplicative Inverse Modulo in International Data Encryption Algorithm? I don't understand on how to perform itâ€¦ For example, let's say I have a value of ...