android 签名

2. 签名
a) Testkey, platform, share, media
b) android\build\target\product\security
c) android:sharedUserId="android.uid.system"，相同的shareuserid可以共享资源
d) /development/tools目录下有个make_key的脚本，通过传入两个参数就可以生成一对签名用的key

rk中有3个签名文件
生成*.pem: openssl genrsa -passout pass:"123456" -out testkey.pem 2048


官方描述
The following commands were used to generate the test key pairs:

development/tools/make_key testkey '/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android@android.com'
development/tools/make_key platform '/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android@android.com'
development/tools/make_key shared '/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android@android.com'
development/tools/make_key media '/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android@android.com'

The following standard test keys are currently included:

testkey -- a generic key for packages that do not otherwise specify a key.
platform -- a test key for packages that are part of the core platform.
shared -- a test key for things that are shared in the home/contacts process.
media -- a test key for packages that are part of the media/download system.

These test keys are used strictly in development, and should never be assumed
to convey any sort of validity. When $BUILD_SECURE=true, the code should not
honor these keys in any context.


signing using the openssl commandline (for boot/system images)
--------------------------------------------------------------

1. convert pk8 format key to pem format
% openssl pkcs8 -inform DER -nocrypt -in testkey.pk8 -out testkey.pem

2. create a signature using the pem format key
% openssl dgst -binary -sha1 -sign testkey.pem FILE > FILE.sig

extracting public keys for embedding
------------------------------------
it's a Java tool
but it generates C code
take a look at commands/recovery/Android.mk
you'll see it running $(HOST_OUT_JAVA_LIBRARIES)/dumpkey.jar