8.1. diffie-hellman-group1-sha1

The "diffie-hellman-group1-sha1" method specifies the Diffie-Hellman key exchange with SHA-1 as HASH, and Oakley Group 2 [RFC2409] (1024-bit MODP Group). This method MUST be supported for interoperability as all of the known implementations currently support it. Note that this method is named using the phrase "group1", even though it specifies the use of Oakley Group 2.