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36

There are different layers of secure transport to consider here: VPNs SSL VPN (including tunnels) IPSec VPN SSL/TLS for individual services IPSec vs SSL VPNs Both SSL and IPSec VPNs are good options, both with considerable security pedigree, although they may suit different applications. IPsec VPNs operate at layer 3 (network), and in a typical ...


30

How can I trust this device that it is not stealing my private keys, or doing MITM attack? Trusting is easy: just do it. Way more complex is not to blindly trust this device but to find actual arguments why you should trust or why you should not trust it: Is this a reputable vendor, do others you trust have experience with this vendor? Does the product ...


24

The cryptography involved in the VPN is designed precisely to keep your data safe even in the situation of an attacker who can intercept all traffic; the best an attacker could do in that situation is to disrupt traffic (namely, cutting off the wires). Both SSL, and IPsec-with-IKE, use cryptography in proper ways, so there should be no qualitative ...


24

There are two main usage modes for IPsec: AH and ESP. AH is only for authentication, so I suppose that you are talking about an ESP tunnel between the two servers. All IP packets get encrypted and authenticated, including some header details such as the source and target ports. There are several encryption and MAC algorithms which can be used with IPsec; AES ...


22

@graham-hill's answer is correct in general but short and pedantically incorrect, so I'll expand upon it. SSH is at the Application level - you can think of it as SSH/TCP/IP, or SSH-over-TCP-over-IP. TCP is the Transport layer in this mix, IP is the Internet layer. Other "Application" protocols include SMTP, Telnet, FTP, HTTP/HTTPS... IPSec is ...


19

The product is a manually configured Orange Pi device. Someone made and configured it. You hope that they knew what they were doing and that they did not install backdoors. With commercial products, you have a base level of communal trust that everyone is trusting the manufacturer and if the vendor did something wrong (intentionally or by accident) then ...


18

Let's clear up some confusion here first. Internet Key Exchange (IKE) is a hybrid protocol, it consists of 3 "protocols" ISAKMP: It's not a key exchange protocol per se, it's a framework on which key exchange protocols operate. Oakley: Describes the "modes" of key exchange (e.g. perfect forward secrecy for keys, identity protection, and authentication) ...


15

Yes and no. SSL offers end-to-end encryption between the application using SSL and the server to which you are connecting. It's a layer 6 protocol and may only provide security for that particular application. In case of IPSec, it works at layer 3. It's mostly used to provide end-to-end encryption between different sites. For instance, if you have several ...


11

Let's define a few things clearly... When you use an asymmetric algorithm like DH, it has a "strength" that relates to the difficulty of breaking through it with the best known attacks. The best known attacks on DH try to solve discrete logarithm with an index calculus variant that has a lot of common elements with the General Number Field Sieve, an integer ...


10

Security Parameter Indexes (SPIs) can mean different things when referring to IKE and IPsec Security Associations (SAs): For IKE two 64-bit SPIs uniquely identify an IKE SA. With IKEv2 the IKE_SA_INIT request will only have the locally unique initiator SPI set in the IKE header, the responder SPI is zero. The responder will set that to a likewise locally ...


9

From Cisco: http://www.ciscopress.com/articles/article.asp?p=25477 Tunnel mode is most commonly used between gateways, or at an end-station to a gateway, the gateway acting as a proxy for the hosts behind it. Transport mode is used between end-stations or between an end-station and a gateway, if the gateway is being treated as a host—for ...


8

The data bits which flow one machine to the other must travel in some way, over wires, optic fiber, radio waves or some other medium. At any point, information can be eavesdropped. The very low-grade attackers will eavesdrop where it is easiest, i.e. close to either end. This is made easy with many WiFi hotspots; it can also be done with wired Ethernet by ...


8

No, you can't. You can't ssh to folders, only to accounts. You might be able to mount the /tmp folder on another machine without a password if the server is running NFS or Samba and has fairly relaxed permissions.


8

RFC 5280 states that "Certificate users MUST be able to handle serialNumber values up to 20 octets. Conforming CAs MUST NOT use serialNumber values longer than 20 octets." Of course one doesn't have to conform... Edit: an octet is 8 bits so if you have 20 octets that's 160 bits...for binary we have base 2 bits => 2^160 = 1.4615016e+48 AKA a really ...


7

To protect packet destinations, you need to abstract the network layer entirely - which usually means some form of encrypted VPN. This would mean no hardware on the local network would know what packets are being transmitted, where to or what they contain. Unfortunately, this doesn't solve the real problem, just moves it upstream. Your VPN/encrypted link ...


7

It is not that the header has to be encrypted in tunnel mode; rather, if the header is not encrypted, it is not really a tunnel. Tunnel mode is about having two routers linked together with an encrypted tunnel. They exchange packets for other hosts. Schematically, router A is the exit router for network netA, and router B is the exit router for network netB....


7

"Security Association" is the big name for whatever a machine A needs to know in order to send IPSec-protected packets to a machine B. Within the memory of A is the information: "with B, packets must use this type of IPSec header (AH or ESP) with these cryptographic algorithms and that specific key". By definition, when machine A talks to machine B and uses ...


7

Is this authentication method simply not supported on windows? Correct. The Windows VPN client simply does not support using Group Security in an IPSec VPN. Additionally, the Cisco IPSec VPN client is EoL, so they don't really support it anymore (preferring customers to pay for AnyConnect SSL VPN licenses). There are some free alternatives out there, as ...


7

For preventing interception and reading of the secret content, encryption algorithms like AES are used. HMACs do not matter at all for this part. Assuming AES (CBC etc.) is secure, an attacker could still intercept what you're sending or receiving, but he can't read it. What he could do, however, is to change the data to something else. Again assuming AES ...


7

TLS was designed to secure only the Application Layer data only. You can use TLS to create a VPN tunnel, but it is not in this way as often. IPSec/ISAKMP was designed to secure the IP, TCP, and Application Layer data. When using IPSec the IPs are encapsulated with an extra layer of the two endpoints for the IPSec tunnel (VPN), and everything at the ...


6

I think it's referring to "hub" as the center of a hub-and-spoke VPN architecture, as shown in this diagram. Later on in the document you linked to, it says: Dynamic—Dynamic crypto maps can only be used in a hub-and-spoke VPN topology. Dynamic crypto map policies allow remote peers to exchange IPsec traffic with a local hub, even if the hub does not ...


6

By default, strongSwan uses its own implementations for cryptographic algorithms. These are provided by e.g. the aes, sha1 and sha2 plugins. The default implementation for public key cryptography (RSA, DH) is provided by the gmp plugin, which relies on libgmp. Enabling the openssl or gcrypt plugins, while not-building or not-loading the default plugins, ...


6

This question brought back some memories of when I created (with the help of a friend) a small tool to detect the presence of NAT in networks. The idea is quite simple (inspired/stolen from the NAT traversal technique in IPSec): You have network segment A and network segment B, and you want to detect the presence of a NAT between them. Send a TCP packet ...


6

Much depends on your scenario. If the two hosts collaborate, just have one of the two send its IP to the other. Optionally hash/encrypt it in order to keep protocol rewriting filters (such as ftp-masq) from rewriting not only the header packet IP but the payload too. Then, if the two addresses don't match, NAT must have been at work. If you only have one ...


6

PPTP is incredibly insecure as you've stated and provides next to no security whatsoever, there are tons of vulnerabilities in it and should be avoided at all costs. You can read more about those vulnerabilities here if you scroll down to Security L2TP should always obviously be used with IPSec because L2TP doesn't actually feature any encryption if you run ...


6

The answer provided in the linked comment isn't very thorough, so here's a better explanation. IPsec is used by itself (sometimes referred to as bare IPsec) all the time; it is commonly used to create a secure transport link between two machines, or to create a tunnel between to different networks / POPs; the former is used (as mentioned) between two ...


6

Update 21 Oct 2017. I found some useful info in RFC 5114 under Section 4 "Security Considerations". Based on this recommendation, we can consider DH Groups 14 and 24 as too weak to protect AES 128 Symmetric Keys - this leaves DH Groups 19 through 21 ECP as the minimum acceptable Diffie Hellman groups for generating AES symmetric keys (128 bit and higher). ...


5

The IP Authentication Header (AH) is used to provide connectionless integrity and data origin authentication for IP datagrams (hereafter referred to as just "authentication"), and to provide protection against replays. This latter, optional service may be selected, by the receiver, when a Security Association is established. (Although the ...


5

It is not "secret", but it is "tamperproof". That may not meet your definition of "secure". Your data is no longer confidential if only AH is used - anyone capturing packets can read your data because it is not encrypted. It is protected against modification, however; AH ensures that data tampering will be detected and discarded. AH does not "inherently ...


5

This probably ought to be moved to security stackexchange, but not because it's specific to a particular security product, but instead it's specific to a specific security protocol. However, I'll try to address the questions anyways. Before I start, I need to explain how IKE and IPSec work together. It's not like TLS (where there is one set of logical ...


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