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Invalid ephemeral DH key size error
Michael Invalid ephemeral DH key size error
Hey there,

Trying to connect to KpyM via ssh from MAC OS X 10.11.5 and get the following error in the logs:

can't read login

ssh info: Client requested invalid ephemeral DH key size 7680 bits, should be 1016...4096

session.exe end

have tried the preferredAuthentications and blowfish solutions.. any ideas?

The server works great connecting from putty on windows


I have exactly the same problem. By any chance, have you figured out a solution?

Same problem here.


KexAlgorithms diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1

to the relevant section of your openssh client's config should fix the issue.

The problem appeared after one of MAC OS updates in 2017.

Generally, there are 2 ways to solve this issue.

1. Edit your ssh_config file and uncomment Ciphers and MACs section:

sudo nano /etc/ssh/ssh_config

Find the strings:
Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc
MACs hmac-md5,hmac-sha1,

After that ssh will work as usual.

2. Add parameters from command line:

ssh -oCiphers=3des-cbc -oMACs=hmac-md5 -l <user>

Hope it helps.


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