While performing a vulnerability assessment, I stumbled upon RIPv1 poisoning routing table attacks. The recommendation is to use RIPv2 with MD5 authentication. The idea is that the routes need to be authenticated by a password before becoming active.

Isn't MD5 broken? I feel unsure in recommending this to the client, is this insecure?


2 Answers 2


MD5 was never broken, but it was discovered there could be generated collisions hence weakening it.

I would suggest OSPFv3, it allows SHA or MD5.

OSPF is not as simple as RIP, it is intended for more complex networkings, but IMHO would be a very good choice complexity/authentication security.

This is a sample cisco config using SHA-512 (source)

interface GigabitEthernet 0/0
 ospfv3 1 ipv4 authentication key-chain ospf-1
 router ospfv3 1
  address-family ipv6 unicast vrf vrf1
   area 1 authentication key-chain ospf-1
   area 1 virtual-link authentication key-chain ospf-1
   area 1 sham-link authentication key-chain ospf-1
   authentication mode deployment     
key chain ospf-1
key 1
   key-string ospf
   cryptographic-algorithm hmac-sha-512

It's not really "broken", just has issues with collisions. It's recommended that you don't use it because it is the unsalted and is very quick to hash. It still would take a very long time to crack. Still, you don't want to use it for passwords if you don't have to.

  • 2
    MD5 passwords can actually be cracked quite quickly. User generated passwords tend to be low-entropy, and there are hashing rigs out there that can "guess" a couple hundred billion passwords per second. Also, MD5 is not "unsalted". Salting is another layer added on top of whatever hashing algorithm you use, so calling any hash unsalted is a bit of a confusion of terms, IMO. Aug 27, 2018 at 17:03
  • The average person doesn't own or can afford a hashing rig. Also, are there not algorithms that apply salts after hashing by themselves?
    – Rocket
    Aug 27, 2018 at 17:07
  • 3
    It doesn't really matter what the average person owns or affords. After all, the average person doesn't know what a hash is to begin with. What matters is what a credible attacker can own and afford. There are enough high-powered cracking rigs out there that you are best off assuming that md5 hashes can be cracked very quickly. At even just a billion hashes per second (a high-end GPU) you can check every 8 character alpha-numeric string in about a day. Aug 27, 2018 at 17:24
  • Some hashing algorithms, especially those designed for passwords, do presume that a salt is being included. Even still though the salt is not inherent to the hashing. bcrypt is just blowfish + fancy keys + adjustable cost + salt. The salt is a simple add-on that can be placed on any hash function. If the only problem with MD5 was that it didn't have a salt, then the simple answer would be: who cares, just add the salt yourself. Aug 27, 2018 at 17:27
  • 1
    Regarding "owns a hashing rig", bear in mind that a GPU instance on AWS is available, on demand, for anybody. It'd be cheaper in the long run to buy your own, but anybody who needs to brute-force a few billion hash inputs can have capable hardware for it in minutes.
    – CBHacking
    Dec 26, 2018 at 1:01

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