SSH key length

Question

SSH

Goodnight!
I noticed a feature of the puttygen program. When generating a key pair SSH2-RSA 2048, the output is a key of 2047 bits
ssh-rsa 2047 dd:92:ac:59:f9:60:e5: ххххххххххххх
But if you generate a key pair on the server - and then load it into puttygen - the key is normal - 2048 bits
What is the reason for such a feature of the loss of one bit during generation?
When generating a keychain of 1024 bits, everything matches the specified key length.



ps test key generated

Answer 1

This feature is with RSA only, there is no such thing on DSA.
More details here:
http://the.earth.li/~sgtatham/putty/0.62/htmldoc/Chapter8.html#puttygen-strength