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[Backport ncs-v3.1-branch] Series of commits that defult to HMAC-SHA512 for X25519 on NRF54L #494

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Merged
merged 3 commits into from
Aug 11, 2025
Merged

[Backport ncs-v3.1-branch] Series of commits that defult to HMAC-SHA512 for X25519 on NRF54L #494

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6198cd4
[nrf fromtree] bootutil: Fix X25519 HMAC-SHA512
de-nordic Jul 29, 2025
7b07ea7
[nrf fromtree] imgtool: Fix x25519 TLV HMAC tag
de-nordic Jul 29, 2025
39c6b14
[nrf noup] zephyr: Enforce HMAC-SHA512 for NRF54L with X25519
de-nordic Jul 30, 2025
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6 changes: 5 additions & 1 deletion boot/bootutil/src/encrypted_psa.c
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Expand Up @@ -43,7 +43,11 @@ static const uint8_t ec_pubkey_oid[] = MBEDTLS_OID_ISO_IDENTIFIED_ORG \
#define HKDF_AES_KEY_SIZE (BOOT_ENC_KEY_SIZE)
/* MAC feed */
#define HKDF_MAC_FEED_INDEX (HKDF_AES_KEY_INDEX + HKDF_AES_KEY_SIZE)
#define HKDF_MAC_FEED_SIZE (32) /* This is SHA independent */
#if !defined(MCUBOOT_HMAC_SHA512)
#define HKDF_MAC_FEED_SIZE (32)
#else
#define HKDF_MAC_FEED_SIZE (64)
#endif
/* Total size */
#define HKDF_SIZE (HKDF_AES_KEY_SIZE + HKDF_MAC_FEED_SIZE)

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1 change: 1 addition & 0 deletions boot/zephyr/Kconfig
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Expand Up @@ -728,6 +728,7 @@ if BOOT_ENCRYPT_X25519 && BOOT_USE_PSA_CRYPTO

choice BOOT_HMAC_SHA
prompt "SHA used for HMAC and HKDF in encryption key exchange"
default BOOT_HMAC_SHA512 if BOOT_ENCRYPT_X25519 && (SOC_NRF54L15_CPUAPP || SOC_NRF54LM20A_ENGA_CPUAPP)
default BOOT_HMAC_SHA256
help
HMAC/HKDF sha algorithm may be selected to synchronize sha
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2 changes: 1 addition & 1 deletion scripts/imgtool/image.py
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Expand Up @@ -444,7 +444,7 @@ def ecies_hkdf(self, enckey, plainkey, hmac_sha_alg):
newpk = X25519PrivateKey.generate()
shared = newpk.exchange(enckey._get_public())
derived_key = HKDF(
algorithm=hmac_sha_alg, length=48, salt=None,
algorithm=hmac_sha_alg, length=16 + hmac_sha_alg.digest_size, salt=None,
info=b'MCUBoot_ECIES_v1', backend=default_backend()).derive(shared)
encryptor = Cipher(algorithms.AES(derived_key[:16]),
modes.CTR(bytes([0] * 16)),
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