2.3 KiB
From https://github.com/pratikd650/Teensy_U2F/blob/master/Teensy_U2F.cpp line 292
Instructions to generate attestation certificate using open ssl https://wiki.openssl.org/index.php/Command_Line_Elliptic_Curve_Operations https://www.guyrutenberg.com/2013/12/28/creating-self-signed-ecdsa-ssl-certificate-using-openssl/ P-256 (also secp256r1) EC key pair is W = dG (Note secp256k1 is Koblitz curve - not P256) d = private key is it 256 bits (32 bytes) G = generator point - it is part of the curve definition W = public key point - it is a (256, 256) bits - 64 bytes
- Generate a key pair - the private key will be saved in PKCS8 format in ecprivkey.pem
openssl ecparam -name prime256v1 -genkey -noout -out ecprivkey.pem
- Dump out the private key in hex format - it will be a 32 byte key
openssl asn1parse -in ecprivkey.pem
- Compute the public key from the private key and the curve
openssl ec -in ecprivkey.pem -pubout -out ecpubkey.pem
- Dump out the public key in hex format - it will be 66 byte - the first two bytes are 00 04,
openssl ec -in ecprivkey.pem -pubout -text
after that is the point W - 32 byte + 32 byte
- Generate a self signed certificate
openssl req -new -x509 -key ecprivkey.pem -out certificate.pem -days 3650
For the Certificate name give a unique certificate name.
- Display the certificate
openssl x509 -in certificate.pem -text -noout
- Convert PEM certificate to DER
openssl x509 -outform der -in certificate.pem -out certificate.der
- Generate a usable c-array for source code
xxd --include certificate.der
Copy output into appropriate array in 'Certificates.cpp', overwriting existing values
- Repeat steps 7 & 8 for public key and private key
So:
openssl asn1parse -in ecprivkey.pem 2>/dev/null | grep 'HEX DUMP' | perl -pe 's/^.*\[HEX DUMP\]:(.+)$/$1/' 2>/dev/null | xxd -r -p > privkey.der && xxd --include privkey.der
openssl ec -in ecprivkey.pem -pubout -text 2>/dev/null | perl -0777 -ne 'print /pub:.+ASN1/sg' 2>/dev/null | sed -e '/pub:/d;/ASN1/d' | perl -pe 's/^\s+(.+):?$/$1/gm' 2>/dev/null | perl -pe 's/\n//' 2>/dev/null | perl -pe 's/(.{2}):?/$1/g' 2>/dev/null | xxd -r -p > pubkey.der && xxd --include pubkey.der
and copy the arrays into the correct arrays in Certificates.cpp.
If any arrays have different lengths than shown in Certificates.hpp, update these too.