4 ms·

I feel like the Dual_EC_DRBG backdoor has given Elliptic Curve Crypto a bad reputation lasting for decades. I guess it's unfair to the technology as a whole, bu

I feel like the Dual_EC_DRBG backdoor has given Elliptic Curve Crypto a bad reputation lasting for decades. I guess it's unfair to the technology as a whole, but somehow RSA just feels safe and battle tested.

chasil 5y ago
The tinyssh server only uses DJB cipher suites; the curve25519-sha256@libssh.org implementation has been in place for quite some time without any major issues. https://www.libssh.org/2013/11/03/openssh-introduces-curve25519-sha256libssh-org-key-exchange/ https://www.libssh.org/2013/11/03/openssh-introduces-curve25... "This algorithm does not rely on NIST-based curves and gives us more security confidence against a possible backdoor in nistp-256 curve. Today is a big day for us because OpenSSH team approved my patch and made curve25519-sha256@libssh.org the default key exchange!" Also, the original RSA keys used in SSH have a sha-1 problem, and have been deprecated. https://www.zdnet.com/article/openssh-to-deprecate-sha-1-logins-due-to-security-risk/ https://www.zdnet.com/article/openssh-to-deprecate-sha-1-log... https://www.openssh.com/releasenotes.html https://www.openssh.com/releasenotes.html This release disables RSA signatures using the SHA-1 hash algorithm by default. This change has been made as the SHA-1 hash algorithm is cryptographically broken, and it is possible to create chosen-prefix hash collisions for <USD$50K [1] For most users, this change should be invisible and there is no need to replace ssh-rsa keys. OpenSSH has supported RFC8332 RSA/SHA-256/512 signatures since release 7.2 and existing ssh-rsa keys will automatically use the stronger algorithm where possible. Incompatibility is more likely when connecting to older SSH implementations that have not been upgraded or have not closely tracked improvements in the SSH protocol.
- hannob 5y ago
  The concerns about the nist curves and the dual ec issue are two completely separate things. Furthermore: > Also, the original RSA keys used in SSH have a sha-1 problem, and have been deprecated. This is wrong. What's correct is that openssh plans to deprecate sha1 signatures, but you can still use your RSA keys with sha2-based signatures.
gurrone 5y ago
Ironically I lately had a payment service provider handing me newly generated ecdsa ssh keys where ed25519 should be supported to the best of my knowledge. And fluxcd moved from rsa to ecdsa by https://github.com/fluxcd/flux2/releases/tag/v0.21.0 https://github.com/fluxcd/flux2/releases/tag/v0.21.0. Kinda strange people are moving on to EC cipher - which is good, but to the cipher which has the NIST/NSA smell.
- chasil 5y ago
  I have upgraded all of my ECDSA host keys to the 521 curve, which has some praise from DJB, unlike the 256 and 384 curves (ssh-keygen -b #: "For ECDSA keys, the -b flag determines the key length by selecting from one of three elliptic curve sizes: 256, 384 or 521 bits"). http://blog.cr.yp.to/20140323-ecdsa.html http://blog.cr.yp.to/20140323-ecdsa.html "To be fair I should mention that there's one standard NIST curve using a nice prime, namely 2^521 - 1; but the sheer size of this prime makes it much slower than NIST P-256."

chasil 5y ago

The tinyssh server only uses DJB cipher suites; the curve25519-sha256@libssh.org implementation has been in place for quite some time without any major issues. https://www.libssh.org/2013/11/03/openssh-introduces-curve25519-sha256libssh-org-key-exchange/ https://www.libssh.org/2013/11/03/openssh-introduces-curve25... "This algorithm does not rely on NIST-based curves and gives us more security confidence against a possible backdoor in nistp-256 curve. Today is a big day for us because OpenSSH team approved my patch and made curve25519-sha256@libssh.org the default key exchange!" Also, the original RSA keys used in SSH have a sha-1 problem, and have been deprecated. https://www.zdnet.com/article/openssh-to-deprecate-sha-1-logins-due-to-security-risk/ https://www.zdnet.com/article/openssh-to-deprecate-sha-1-log... https://www.openssh.com/releasenotes.html https://www.openssh.com/releasenotes.html This release disables RSA signatures using the SHA-1 hash algorithm by default. This change has been made as the SHA-1 hash algorithm is cryptographically broken, and it is possible to create chosen-prefix hash collisions for <USD$50K [1] For most users, this change should be invisible and there is no need to replace ssh-rsa keys. OpenSSH has supported RFC8332 RSA/SHA-256/512 signatures since release 7.2 and existing ssh-rsa keys will automatically use the stronger algorithm where possible. Incompatibility is more likely when connecting to older SSH implementations that have not been upgraded or have not closely tracked improvements in the SSH protocol.

hannob 5y ago
The concerns about the nist curves and the dual ec issue are two completely separate things. Furthermore: > Also, the original RSA keys used in SSH have a sha-1 problem, and have been deprecated. This is wrong. What's correct is that openssh plans to deprecate sha1 signatures, but you can still use your RSA keys with sha2-based signatures.

gurrone 5y ago

Ironically I lately had a payment service provider handing me newly generated ecdsa ssh keys where ed25519 should be supported to the best of my knowledge. And fluxcd moved from rsa to ecdsa by https://github.com/fluxcd/flux2/releases/tag/v0.21.0 https://github.com/fluxcd/flux2/releases/tag/v0.21.0. Kinda strange people are moving on to EC cipher - which is good, but to the cipher which has the NIST/NSA smell.

chasil 5y ago
I have upgraded all of my ECDSA host keys to the 521 curve, which has some praise from DJB, unlike the 256 and 384 curves (ssh-keygen -b #: "For ECDSA keys, the -b flag determines the key length by selecting from one of three elliptic curve sizes: 256, 384 or 521 bits"). http://blog.cr.yp.to/20140323-ecdsa.html http://blog.cr.yp.to/20140323-ecdsa.html "To be fair I should mention that there's one standard NIST curve using a nice prime, namely 2^521 - 1; but the sheer size of this prime makes it much slower than NIST P-256."