Need Help with Dropbear Export Questions

Matt Johnston matt at ucc.asn.au
Thu Apr 19 10:51:15 WST 2007


On Thu, Apr 19, 2007 at 12:40:56AM +0000, Edward Wang wrote:
> I am currently in the process of trying to obtain clearance to export some 
> custom computers out of the U.S.  The computers have Dropbear, and the lawyers 
> have questions about Dropbear encryption that I can't answer.   Unfortunately, 
> I can not find any documentation online with the answers either.  I'd 
> appreciate it if anyone can give the answers or can point me to where I can 
> find the answers. 

The SSH2 specification at
http://www.ietf.org/rfc/rfc4253.txt is probably a reasonable
start. See inline for a list more specific to Dropbear. Hmm,
I need to get some glossy marketing pamphlets to print :)

> 1.      Describe the symmetric and asymmetric encryption
> algorithms and key lengths and how the algorithms are used
> (e.g., 56-bit DES, 168-bit DES, 128-bit RC4, 448-bit
> Blowfish, etc.).  Specify which encryption modes are
> supported (e.g., cipher feedback mode or cipher block
> chaining mode).  For any asymmetric algorithms, please
> specify whether the security of the algorithm is based
> upon any of the following: (a) factorization of integers
> in excess of 512 bits (e.g., RSA); (b) computation of
> discrete logarithms in a multiplicative group of a finite
> field of size greater than 512 bits (e.g., Diffie-Hellman
> over Z/pZ); or (c) discrete logarithms in a group other
> than mentioned above in excess of 112 bits (e.g.,
> Diffie-Hellman over an elliptic curve). 

Symmetric algos all in cipher block chaining (CBC) mode:
168-bit 3DES
256- or 128-bit AES
128-bit Blowfish 
128- or 256-bit Twofish

Asymmetric algos:
Diffie-Hellman, computing discrete logarithms (1024-bit)

(RSA and DSS are used but not for encryption)


> 2.      State the key management algorithms, including
> modulus sizes, that are supported (e.g., 512-bit RSA,
> 1024-bit Diffie-Hellman, etc.). 

Diffie-Hellman   1024-bit
Signing only:
RSA   512- to 4096-bit
DSA   512- to 4096-bit


Hopefully that's of use, good luck.

Matt


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