From 28c5f596ae3d1790cdc96fa5fc7370f934abfb2e Mon Sep 17 00:00:00 2001 From: David Gstir Date: Wed, 3 Apr 2024 09:21:22 +0200 Subject: docs: trusted-encrypted: add DCP as new trust source Update the documentation for trusted and encrypted KEYS with DCP as new trust source: - Describe security properties of DCP trust source - Describe key usage - Document blob format Co-developed-by: Richard Weinberger Signed-off-by: Richard Weinberger Co-developed-by: David Oberhollenzer Signed-off-by: David Oberhollenzer Signed-off-by: David Gstir Reviewed-by: Jarkko Sakkinen Reviewed-by: Bagas Sanjaya Signed-off-by: Jarkko Sakkinen --- security/keys/trusted-keys/trusted_dcp.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'security/keys/trusted-keys/trusted_dcp.c') diff --git a/security/keys/trusted-keys/trusted_dcp.c b/security/keys/trusted-keys/trusted_dcp.c index 16c44aafeab3..b5f81a05be36 100644 --- a/security/keys/trusted-keys/trusted_dcp.c +++ b/security/keys/trusted-keys/trusted_dcp.c @@ -19,6 +19,25 @@ #define DCP_BLOB_VERSION 1 #define DCP_BLOB_AUTHLEN 16 +/** + * DOC: dcp blob format + * + * The Data Co-Processor (DCP) provides hardware-bound AES keys using its + * AES encryption engine only. It does not provide direct key sealing/unsealing. + * To make DCP hardware encryption keys usable as trust source, we define + * our own custom format that uses a hardware-bound key to secure the sealing + * key stored in the key blob. + * + * Whenever a new trusted key using DCP is generated, we generate a random 128-bit + * blob encryption key (BEK) and 128-bit nonce. The BEK and nonce are used to + * encrypt the trusted key payload using AES-128-GCM. + * + * The BEK itself is encrypted using the hardware-bound key using the DCP's AES + * encryption engine with AES-128-ECB. The encrypted BEK, generated nonce, + * BEK-encrypted payload and authentication tag make up the blob format together + * with a version number, payload length and authentication tag. + */ + /** * struct dcp_blob_fmt - DCP BLOB format. * -- cgit v1.2.3