crypto/signature/ksign-publickey.c: key.h: No such file or directory

crypto/signature/ksign-publickey.c: key.h: No such file or directory

When I try to compile RHEL kernel 2.6.32-642, I met following errors:

crypto/signature/ksign-publickey.c:2:17: error: key.h: No such file or directory
crypto/signature/ksign-publickey.c: In function ‘ksign_init’:
crypto/signature/ksign-publickey.c:10: error: ‘ksign_def_public_key’ undeclared (first use in this function)
crypto/signature/ksign-publickey.c:10: error: (Each undeclared identifier is reported only once
crypto/signature/ksign-publickey.c:10: error: for each function it appears in.)
crypto/signature/ksign-publickey.c:11: error: ‘ksign_def_public_key_size’ undeclared (first use in this function)
make[2]: *** [crypto/signature/ksign-publickey.o] Error 1
make[1]: *** [crypto/signature] Error 2
make: *** [crypto] Error 2

After google it, I found the solution is:

run make menuconfig.
1) Select "Enable loadable module support", then "Module signature verification (EXPERIMENTAL)". Disable it.
2) Then go back to the main menu, select "Cryptographic API" then "In-kernel signature checker (EXPERIMENTAL)" and disable that one too.
Then go back again, save your config and make your kernel. At least, it will pass this phase successfully