服务器评测
对于千兆网来说，带宽大致为125M/s，scp的速度约为40M/s,对于需要全量恢复数据库的时候（300G 左右的量），需要2个小时左右，很不能接受这种情况；
加快SCP传输速度需要考虑以下几点：
1、ssh加密算法的改变；（加密算法越弱速度越快在IDC内网间可以考虑使用）
2、数据完整校验方式改变；（MACs Message authentication code）
3、是否启用压缩；
4、磁盘性能问题；
man scp 可调整速率的大多在算法上，（亲测-B batch mode 对传输影响不大）
-c cipher -o 完整性校验
ssh -v 调试ssh连接
关于以上问题的测试数据可参考：http://www.linuxidc.com/Linux/2014-01/95497.htm
加密算法可以采用 scp -c aes192-cbc
数据完整性校验采用 scp -o ‘MACs umac-64@openssh.com’ 关于此哈希算法
值得一提的是压缩，只要压缩后节省的传输时间大于压缩本身的时间；
压缩往往适用于： 网速慢；数据中大量重复、空洞的； 而对于压缩比很低的数据不建议使用SSH的传输压缩方式；最好在本地进行并行压缩后再传输；
加快压缩可以参考以下命令：
scp -c aes192-cbc -o “MACs umac-64@openssh.com”
Network Working Group D. Miller
Internet-Draft P. Valchev
Intended status: Standards Track OpenSSH
Expires: March 6, 2008 September 3, 2007
The use of UMAC in the SSH Transport Layer Protocol
draft-miller-secsh-umac-01.txt
Status of this Memo
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This memo describes the use of the UMAC Message Authentication Code
in the SSH transport protocol.
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Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . . 3
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. MAC calculation . . . . . . . . . . . . . . . . . . . . . . . . 3
4. New MAC methods . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. umac-32 . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. umac-64 . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.3. umac-96 . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.4. umac-128 . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5
Intellectual Property and Copyright Statements . . . . . . . . . . 6
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1. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Overview
SSH [RFC4251] is a popular protocol for secure remote login and data
transfer on the Internet. Among the security properties that SSH
offers is integrity of communication against active adversaries.
This integrity is provided in the SSH transport protocol [RFC4253]
through the use of a per-packet Message Authentication Code (MAC).
This memo describes the use of the UMAC Message Authentication Code
[RFC4418] in the SSH transport protocol. UMAC offers improved
performance over the current HMAC-based MACs supported by SSH.
Furthermore, UMAC represents a different cryptographic approach to
message authentication to that of HMAC, and its use in SSH would
provide a diversity that may be of benefit if HMAC or one of its
underlying hash algorithms is found to be vulnerable to a new attack.
UMAC offers a choice of four authentication tag sizes: 32, 64, 96 and
128 bits. This allows users to trade between fast, compact tags and
longer tags that are slower to generate but offer better security.
These four tag sizes are represented in the new MAC methods
introduced in this memo: "umac-32", "umac-64", "umac-96" and "umac-
128".
3. MAC calculation
Message authentication tags in the SSH transport protocol are
specified to be calculated over the packet sequence number followed
by the entire unencrypted packet:
mac = MAC(key, sequence_number || unencrypted_packet)
However, UMAC accepts a nonce as an explicit input to MAC
calculation. In order for the security proofs that accompany UMAC to
apply, this nonce must never be repeated under a given key. In the
context of the SSH protocol, this may be achieved by using the packet
sequence number as the nonce. The sequence number is guaranteed to
be unique over the life of the MAC key by the requirement that
implementations perform a key re-exchange before the sequence number
wraps (section 9.3.3 of [RFC4251]).
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To use the sequence number as the MAC nonce, it is encoded into a SSH
protocol uint64 (as described in section 5 of [RFC4251]) and it is
supplied to the UMAC algorithm instead of prepending it to the packet
to be authenticated:
mac = UMAC(key, sequence_number, unencrypted_packet)
Where UMAC is one of the UMAC-32, UMAC-64, UMAC-96 or UMAC-128
algorithms specified in [RFC4418], section 4.2, using the default
underlying block cipher of AES-128.
4. New MAC methods
This memo introduces four new MAC methods, one for each UMAC
authentication tag length specified in [RFC4418]: "umac-32",
"umac-64", "umac-96" and "umac-128".
4.1. umac-32
Calculate message authentication tags using the UMAC-32 algorithm
specified in [RFC4418], section 4.2.
4.2. umac-64
Calculate message authentication tags using the UMAC-64 algorithm
specified in [RFC4418], section 4.2.
4.3. umac-96
Calculate message authentication tags using the UMAC-96 algorithm
specified in [RFC4418], section 4.2.
4.4. umac-128
Calculate message authentication tags using the UMAC-128 algorithm
specified in [RFC4418], section 4.2.
5. Security Considerations
As mentioned above, it is imperative that implementations perform a
re-keying operation before reusing a packet sequence number as a UMAC
nonce. Implementations conforming to [RFC4251] are already required
to do this.
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6. IANA Considerations
IANA must assign the MAC Algorithm Names "umac-32", "umac-64",
"umac-96" and "umac-128".
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
Protocol Architecture", RFC 4251, January 2006.
[RFC4253] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, January 2006.
[RFC4418] Krovetz, T., "UMAC: Message Authentication Code using
Universal Hashing", RFC 4418, March 2006.
Authors' Addresses
Damien Miller
OpenSSH
Email: djm@openssh.com
Peter Valchev
OpenSSH
Email: pvalchev@openssh.com
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