# number of blocks, and size of padding at 64bit

A message has 2003 characters, encrypted using a block cipher of 64 bits. What is the size of the padding and the number of blocks?

I tried this, but I'm sure it's not the right thing:

• 2003 mod 64 = 19, this is the number of bits that needs padding.
• 2003 / 64 = 31, this is the number of complete blocks, this + 1 = 32 is the total number of blocks.
• @poncho Presumably a character is supposed to have 8 bits. So you need to either compute 2003 * 8 % 64 (in bits) or 2003 % 8 (in bytes). – CodesInChaos Nov 30 '16 at 18:10
• @CodesInChaos: sorry about that; somehow, I read that as '2003 bits'... – poncho Nov 30 '16 at 18:29