椭圆曲线（ECC）支持¶
Compatible Nitrokeys |
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|---|---|---|---|---|---|---|---|
✓ active |
⨯ inactive |
✓ active |
✓ active |
⨯ inactive |
✓ active |
⨯ inactive |
⨯ inactive |
RSA-2048变得越来越不安全了¶
出于安全考虑，德国联邦信息安全办公室（Bundesamt für Sicherheit in der Informationstechnik, BSI）不再建议在2023年之后使用长度为2048位的RSA密钥` <https://www.bsi.bund.de/SharedDocs/Downloads/EN/BSI/Publications/TechGuidelines/TG02102/BSI-TR-02102-1.pdf>`__。这意味着在可预见的未来，更长的密钥将需要投入使用。假设使用期为5年，已经有必要产生更长的密钥了。然而，3072位或4096位的较长RSA密钥的速度明显较慢。由于这个原因，新的Nitrokey Storage 2和Pro 2（即集成的OpenPGP卡3.3版）支持通过`椭圆曲线加密法（ECC）<https://en.wikipedia.org/wiki/Elliptic-curve_cryptography>`__加密。这种方法被认为是用较小的ECC密钥和较长的RSA密钥一样安全，而且速度也相当快。
椭圆曲线加密法的基础知识¶
与RSA相比，椭圆曲线加密法有许多不同的形式（所谓的曲线）。值得注意的是，`NSA参与了<https://www.schneier.com/essays/archives/2007/11/did_nsa_put_a_secret.html>`__在NIST曲线的开发。即使没有证据表明曲线中存在后门，使用某种曲线也会带来信任问题。幸运的是，新的Nitrokey Storage 2和Pro 2支持两种曲线，即NIST和Brainpool。在下面的内容中，我们将使用Brainpool 曲线。`这篇文章<https://arstechnica.com/information-technology/2013/10/a-relatively-easy-to-understand-primer-on-elliptic-curve-cryptography/>`__为获得对椭圆曲线加密法的一般理解提供了一个很好的切入点。
系统要求¶
为了创建基于椭圆曲线的钥匙，需要Nitrokey Storage 2 / Pro 2和GnuPG 2.1.17版或更高版本。
You can read Nitrokey's OpenPGP Card version via gpg2 --card-status:
> gpg2 --card-status
Reader ...........: 20A0:...
Application ID ...: D276...
Version ..........: 3.3
...
The Version field represents the version of the OpenPGP Card integrated in the Nitrokey — in this case it is 3.3 as needed for Elliptic-curve cryptography. OpenPGP Card version 2.2 doesn't support ECC.
你可以通过``gpg2 --version``了解GnuPG的安装版本。至少需要2.1.16版本。最新的Windows版GnuPG可以在`这里<https://www.gpg4win.org/>`__，最新的MacOS版可以在`这里<https://gpgtools.org/>`__找到。GNU/Linux发行版Ubuntu（从18.04开始）、Debian（从Stretch开始）、Arch Linux、Fedora（从26版开始）和openSUSE Tumbleweed中都包含了合适的GnuPG版本。在这篇文章的末尾，有如何在旧版Ubuntu上手动更新GnuPG的说明。
重要
GnuPG 2.0仍在使用，但对它的支持已在2017年停止。所有通信伙伴必须使用GnuPG 2.1或更新版本，通过ECC进行电子邮件加密，否则可能出现不兼容问题。因此，你应该只使用ECC，如果你确定你将能够规避这个问题。
在Nitrokey Storage 2 / Pro 2上生成钥匙¶
Once these requirements are fulfilled, you can get started. (Warning: existing keys will be overwritten in the process!) You now have two options. The first option is to create the key directly on the Nitrokey Storage 2 / Pro 2. The benefit here is that the key will never be outside the device and as such can never be read out. The second option is to import a previously locally generated key. The advantage in this case is that you can securely store a backup of the key, which can then be restored in case the Nitrokey is lost. Only the first option is described below. In order to create a key with backup, you can access the following instructions and use this general information to transfer the key to the Nitrokey.
在GnuPG中，已经有一个 "生成 "命令，可以用来在设备上轻松地创建钥匙。但是，目前还不能直接选择钥匙的类型，所以必须首先准备好钥匙。我们使用以下命令来实现这一点。
> gpg-connect-agent "SCD SETATTR KEY-ATTR --force 1 19 brainpoolP256r1" /bye
> gpg-connect-agent "SCD SETATTR KEY-ATTR --force 2 18 brainpoolP256r1" /bye
> gpg-connect-agent "SCD SETATTR KEY-ATTR --force 3 19 brainpoolP256r1" /bye
另外，也可以选择其他曲线，如下一节所述。
现在我们输入``gpg2 --card-edit``，看到brainpoolP256r1在 "密钥属性 "下而不是rsa2048。
> gpg2 --card-edit
Reader ...........: 20A0:4109:0000000000000:0
Application ID ...: D276000124010303000500005F100000
Version ..........: 3.3
Manufacturer .....: ZeitControl
Serial number ....: 00005F10
Name of cardholder: [not set]
Language prefs ...: [not set]
Sex ..............: unspecified
URL of public key : [not set]
Login data .......: [not set]
Signature PIN ....: forced
Key attributes ...: brainpoolP256r1 brainpoolP256r1 brainpoolP256r1
Max. PIN lengths .: 64 64 64
PIN retry counter : 3 0 3
Signature counter : 0
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]
然后我们创建密钥。
gpg/card> admin
Admin commands are allowed
gpg/card> generate
Make off-card backup of encryption key? (Y/n) n
Please note that the factory settings of the PINs are
PIN = '123456' Admin PIN = '12345678'
You should change them using the command --change-pin
Please specify how long the key should be valid.
0 = key does not expire
<n> = key expires in n days
<n>w = key expires in n weeks
<n>m = key expires in n months
<n>y = key expires in n years
Key is valid for? (0)
Key does not expire at all
Is this correct? (y/N) y
GnuPG needs to construct a user ID to identify your key.
Real name: Jane Doe
Email address: jane.doe@example.org
Comment:
You selected this USER-ID:
"Jane Doe <jane.doe@example.org>"
Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? O
gpg: key 7F8C68E1B084E169 marked as ultimately trusted
gpg: revocation certificate stored as '/home/jane/.gnupg/openpgp-revocs.d/F8C00BC1636A7D7604A31A877F8C68E1B084E169.rev'
public and secret key created and signed.
Nitrokey现在采用了椭圆曲线加密法，而不是RSA密钥，可以照常使用。
可用的曲线¶
在上述程序中，我们选择了Brainpool的曲线。另外，也可以使用NIST曲线。配置工作按以下方式进行。
> gpg-connect-agent "SCD SETATTR KEY-ATTR --force 1 19 nistp256" /bye
> gpg-connect-agent "SCD SETATTR KEY-ATTR --force 2 18 nistp256" /bye
> gpg-connect-agent "SCD SETATTR KEY-ATTR --force 3 19 nistp256" /bye
Ubuntu上GnuPG的更新¶
The following steps are needed only if you are running a Ubuntu version older than 18.04. You can install GnuPG 2.1.18 on such system with the commands below. This involves newer Debian packages, which is the easiest option. This approach has been tested successfully on Ubuntu 17.10 and propbably works on 16.04 as well. However, the occurence of problems during usage can't be excluded.
$ mkdir gnupg_tmp
$ cd gnupg_tmp
$ wget http://ftp.debian.org/debian/pool/main/g/gnupg2/gnupg_2.1.18-8~deb9u1_amd64.deb
$ wget http://ftp.debian.org/debian/pool/main/g/gnupg2/dirmngr_2.1.18-8~deb9u1_amd64.deb
$ wget http://ftp.debian.org/debian/pool/main/g/gnupg2/gnupg-agent_2.1.18-8~deb9u1_amd64.deb
$ wget http://ftp.debian.org/debian/pool/main/g/gnupg2/scdaemon_2.1.18-8~deb9u1_amd64.deb
$ sudo dpkg -i *
$ cd ..
$ rm -rf gnupg_tmp
如果你想撤消安装，你必须执行以下命令。
$ sudo dpkg --remove --force-depends gnupg dirmngr gnupg-agent scdaemon
# (removes manually installed packages)
$ sudo apt-get install gnupg dirmngr gnupg-agent scdaemon
# (installs the appropriate packages from regular package repositories)