Commit 5bcfeaff by Richard van der Hoff

### Update olm.md

parent a9c7bde4
 ... @@ -10,13 +10,13 @@ $\parallel$ appears on the right hand side of an $=$ it means that ... @@ -10,13 +10,13 @@ $\parallel$ appears on the right hand side of an $=$ it means that the inputs are concatenated. When $\parallel$ appears on the left hand the inputs are concatenated. When $\parallel$ appears on the left hand side of an $=$ it means that the output is split. side of an $=$ it means that the output is split. When this document uses $ECDH\left(K_A,\,K_B\right)$ it means that each When this document uses $\operatorname{ECDH}\left(K_A,K_B\right)$ it means party computes a Diffie-Hellman agreement using their private key and the that each party computes a Diffie-Hellman agreement using their private key remote party's public key. and the remote party's public key. So party $A$ computes $ECDH\left(K_B^{public},\,K_A^{private}\right)$ So party $A$ computes $\operatorname{ECDH}\left(K_B^{public},K_A^{private}\right)$ and party $B$ computes $ECDH\left(K_A^{public},\,K_B^{private}\right)$. and party $B$ computes $\operatorname{ECDH}\left(K_A^{public},K_B^{private}\right)$. Where this document uses $HKDF\left(salt,\,IKM,\,info,\,L\right)$ it Where this document uses $\operatorname{HKDF}\left(salt,IKM,info,L\right)$ it refers to the [HMAC-based key derivation function][] with a salt value of refers to the [HMAC-based key derivation function][] with a salt value of $salt$, input key material of $IKM$, context string $info$, $salt$, input key material of $IKM$, context string $info$, and output keying material length of $L$ bytes. and output keying material length of $L$ bytes. ... @@ -35,10 +35,12 @@ HMAC-based Key Derivation Function using [SHA-256][] as the hash function ... @@ -35,10 +35,12 @@ HMAC-based Key Derivation Function using [SHA-256][] as the hash function math math \begin{aligned} \begin{aligned} S&=ECDH\left(I_A,\,E_B\right)\;\parallel\;ECDH\left(E_A,\,I_B\right)\; S&=\operatorname{ECDH}\left(I_A,E_B\right)\;\parallel\; \parallel\;ECDH\left(E_A,\,E_B\right)\\ \operatorname{ECDH}\left(E_A,I_B\right)\;\parallel\; \operatorname{ECDH}\left(E_A,E_B\right)\\ R_0\;\parallel\;C_{0,0}&= R_0\;\parallel\;C_{0,0}&= HKDF\left(0,\,S,\,\text{"OLM\_ROOT"},\,64\right) \operatorname{HKDF}\left(0,S,\text{OLM\_ROOT"},64\right) \end{aligned} \end{aligned}   ... @@ -55,12 +57,13 @@ info. ... @@ -55,12 +57,13 @@ info. math math \begin{aligned} \begin{aligned} R_i\;\parallel\;C_{i,0}&=HKDF\left( R_i\;\parallel\;C_{i,0}&= R_{i-1},\, \operatorname{HKDF}\left( ECDH\left(T_{i-1},\,T_i\right),\, R_{i-1}, \text{"OLM\_RATCHET"},\, \operatorname{ECDH}\left(T_{i-1},T_i\right), 64 \text{OLM\_RATCHET"}, \right) 64 \right) \end{aligned} \end{aligned}   ... @@ -72,7 +75,7 @@ previous chain key as the key. ... @@ -72,7 +75,7 @@ previous chain key as the key. math math \begin{aligned} \begin{aligned} C_{i,j}&=HMAC\left(C_{i,j-1},\,\text{"\x02"}\right) C_{i,j}&=\operatorname{HMAC}\left(C_{i,j-1},\text{\char\\x02"}\right) \end{aligned} \end{aligned}   ... @@ -86,7 +89,7 @@ by Bob to encrypt messages. ... @@ -86,7 +89,7 @@ by Bob to encrypt messages. math math \begin{aligned} \begin{aligned} M_{i,j}&=HMAC\left(C_{i,j},\,\text{"\x01"}\right) M_{i,j}&=\operatorname{HMAC}\left(C_{i,j},\text{\char\\x01"}\right) \end{aligned} \end{aligned}   ... @@ -263,7 +266,7 @@ message key using [HKDF-SHA-256][] using the default salt and an info of ... @@ -263,7 +266,7 @@ message key using [HKDF-SHA-256][] using the default salt and an info of math math \begin{aligned} \begin{aligned} AES\_KEY_{i,j}\;\parallel\;HMAC\_KEY_{i,j}\;\parallel\;AES\_IV_{i,j} AES\_KEY_{i,j}\;\parallel\;HMAC\_KEY_{i,j}\;\parallel\;AES\_IV_{i,j} &= HKDF\left(0,\,M_{i,j},\text{"OLM\_KEYS"},\,80\right) \\ &= \operatorname{HKDF}\left(0,M_{i,j},\text{OLM\_KEYS"},80\right) \end{aligned} \end{aligned}   ... ...
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