FIGURE 21.

An example of the Ripple trust graph before (left) and after (right) Sarah uses rippling to send 50 USD to Bob. On the (left) network, Sarah has two paths that connect her to Bob: (1) Bob $\to$ Alice $\to$ Sarah and (2) Bob $\to$ John $\to$ Tim $\to$ Sarah. However, in the first path that traverses two trust lines, the trust line between Sarah and Alice has a max limit of 20 USD (2 USD of which is already used), which is less than the 50 USD that Sarah wants to send. As a result, Sarah cannot use the first path to send all 50 USD. The second path is longer than the first because it traverses three trust lines; however, the limits allow the 50 USD transfer. Sarah uses the second path for rippling. Owed amounts (values above edges) are increased by the transferred amount: 50 USD. Sarah needs to consider updated (right) values in future transactions; she can no longer send 50 USD to Bob because the trust line John $\to$ Tim has a current capacity of USD 100 − USD 75 = USD 25 only. The updated (increased) amounts imply that after the payment, Sarah owes 50 USD to Tim, who owes 75 USD to John, who owes 65 USD to Bob. (a) Trust lines. Before Sarah sends any currency, the Ripple trust graph includes five nodes and five trust lines. (b) Payment. After the rippling, owed amounts are updated and shown in red rectangles