Microsoft added several extensions to its own SMB implementation. For example, it added NTLM, followed by NTLMv2 authentication protocols, in order to address security weakness in the original LAN Manager authentication. LAN Manager authentication was implemented based on the original legacy SMB specification's requirement to use IBM "LAN Manager" passwords, but implemented DES in a flawed manner that allowed passwords to be cracked. Later, Kerberos authentication was also added. The NT 4.0 Domain logon protocols initially used 40-bit encryption outside of the United States, because of export restrictions on stronger 128-bit encryption (subsequently lifted in 1996 when President Bill Clinton signed Executive Order 13026). Opportunistic locking support has changed with each server release.