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- Update ECDH output to use SHA512 instead of SHA256

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- Specify HMAC_DRBG security strength
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Matt David 2016-05-11 11:19:30 -07:00
parent 3cf25a7594
commit e1d74be3b6
1 changed files with 5 additions and 3 deletions
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@ -308,13 +308,14 @@ For the following we assume the Sender already knows the Receiver's public key,
===ECDH Point Generation and AES-256 (GCM Mode) Setup===
'''NOTE''': AES-256-GCM is used because it provides authenticated encryption facilities, thus negating the need for a separate message hash for authentication.
* Generate the '''secret point''' using [https://en.wikipedia.org/wiki/Elliptic_curve_Diffie–Hellman ECDH] using the local entity's private key and the remote entity's public key as inputs.
* Initialize [http://csrc.nist.gov/publications/nistpubs/800-90A/SP800-90A.pdf HMAC_DRBG]
** Use '''SHA256(secret point's X value)''' for Entropy
* Generate the '''secret point''' using [https://en.wikipedia.org/wiki/Elliptic_curve_Diffie–Hellman ECDH] using the local entity's private key and the remote entity's public key as inputs
* Initialize [http://csrc.nist.gov/publications/nistpubs/800-90A/SP800-90A.pdf HMAC_DRBG]
** Use '''SHA512(secret point's X value in Big-Endian bytes)''' for Entropy
** Use the given message's '''nonce''' field for Nonce
* Initialize AES-256 in GCM Mode
** Initialize HMAC_DRBG with Security Strength of 256 bits
** Use HMAC_DRBG.GENERATE(32) as the Encryption Key (256 bits)
** Use HMAC_DRBG.GENERATE(12) as the Initialization Vector (IV) (96 bits)
@ -380,3 +381,4 @@ The following diagram shows a sample flow in which one mobile client is sending
* [https://tools.ietf.org/html/rfc6979 RFC6979]
* [https://en.bitcoin.it/wiki/Address_reuse Address Reuse]
* [http://csrc.nist.gov/publications/fips/fips180-4/fips-180-4.pdf FIPS 180-4 (Secure Hash Standard)]
* [https://github.com/bitcoin-core/secp256k1/blob/master/src/modules/ecdh/main_impl.h libsecp256k1 ECDH Implementation]