openSSH: configure ciphers.

[Sunil K. Vallamkonda]

I see that:
SSH uses the following ciphers for encryption: 
 Cipher           SSH1        SSH2
 DES              yes         no
 3DES             yes         yes
 IDEA             yes         no
 Blowfish         yes         yes
 Twofish          no          yes
 Arcfour          no          yes
 Cast128-cbc      no          yes


Two ques re: sshd:

1) Using openssh, how do I configure which
   set of ciphers to use from above set for SSH1 and SSH2 ?
   Does "yes" above mean must or an option (configurable)?
  
2) Does SSH2 use DES and 3DES or it is DES or 3DES ?
   If latter, can I specify SSH2 with DES ?

Thank you.