There exists an explicit bijection (due to Cayley, that has built up a very nice table to describe this) between the positive roots of the Latticelattice $E_7$ and $\mathbb{F}_2^6/{0}$$\mathbb{F}_2^6 \setminus \{0\}$ (where $\mathbb{F}_2$ is the field with two elements. Btw, this also preserves orthogonality. There is also a relation between $E_8$ and $\mathbb{F}_2^8/{0}$$\mathbb{F}_2^8 \setminus \{0\}$. Is there an explicit description of the features of this relation in the literature?