Patient provides to HAC the address, H(F₁), of his EMR in IPFS as well as the key allowing to decrypt it

P.1 Patient $\to$ HAC : H(F₁); ${\left\{k\right\}}_{k_c}$

HAC retrieves EMR from IPFS and reads its DID

P.2 HAC $\to$ IPFS : H(F₁)

P.3 IPFS $\to$ HAC : $\underset{F_1}{\underbrace{\underset{M}{\underbrace{DID,{\left\{EMR\right\}}_k}},{\left\{H\left(M\right)\right\}}_{k_p^{-1}}}}$

HAC retrieves the key k_b associated to DID from Indy

P.4 HAC $\to$ Indy : DID

P.5 Indy $\to$ HAC : DID, k_b, ${\left\{H\left(DID,k_b\right)\right\}}_{k_p^{-1}}$

HAC challenges Patient to prove that he is the owner of k_b

P.6 HAC $\to$ Patient : DID, N_c

P.7 Patient $\to$ Patient—USB : H(DID, N_c)

P.8 Patient—USB $\to$ Patient : ${\left\{H\left(DID,N_c\right)\right\}}_{k_b^{-1}}$

P.9 Patient $\to$ HAC : ${\left\{H\left(DID,N_c\right)\right\}}_{k_b^{-1}}$