Communications Source Authentication

1 . A method performed by data processing apparatus, the method comprising:

receiving a symbol over a particular communications channel;

decrypting the symbol using a decryption key that is assigned to a particular endpoint that is assigned the particular communications channel;

computing a measure of error for the decrypted symbol;

determining whether the measure of error exceeds a threshold error measure;

in response to determining that the measure of error exceeds the threshold error measure, identifying the decrypted symbol as a symbol from a different endpoint; and

in response to determining that the measure of error does not exceed the threshold error measure:

identifying the decrypted symbol as a valid symbol transmitted by the particular endpoint; and

logging the valid symbol.

2 . The method of claim 1 , further comprising:

generating, by the particular endpoint, the symbol to include payload data and error correction data;

encrypting, by the particular endpoint, the symbol using an encryption key that is assigned to the particular endpoint; and

transmitting, by the particular endpoint, the encrypted symbol over the particular communications channel.

3 . The method of claim 2 , wherein:

generating the symbol comprises inserting an error correcting code into the payload data; and

encrypting the symbol comprises encrypting the symbol following insertion of the error correcting code.

4 . The method of claim 1 , wherein:

receiving a symbol comprises receiving a plurality of different symbols over a plurality of different communications channels, each different communications channel being assigned to a different endpoint; and

decrypting the symbol comprises, for each of the different communications channels, decrypting the symbol using a decryption key that is assigned to the endpoint to which the communications channel is assigned.

5 . The method of claim 4 , further comprising retrieving, for each different endpoint, a different decryption key that is assigned to the different endpoint.

6 . The method of claim 1 , wherein decrypting the symbol comprises decrypting the symbol with a symmetric key that has been assigned to the particular endpoint.

7 . The method of claim 1 , wherein:

computing a measure of error comprises computing a bit error rate for the decrypted symbol; and

determining whether the measure of error exceeds a threshold error measure comprises determining whether the bit error rate exceeds a threshold bit error rate.

8 . The method of claim 1 , wherein receiving a symbol from a particular endpoint comprises receiving the symbol from a particular meter over a particular channel of a power line communications network.

9 . The method of claim 8 , wherein decrypting the symbol comprises decrypting the symbol with a decryption key that is assigned to the particular meter.

10 . A method performed by data processing apparatus, the method comprising:

receiving a symbol over a particular communications channel;

decrypting the symbol using a decryption key that is assigned to a particular endpoint that has been assigned to communicate over the particular communications channel;

determining that the symbol was transmitted by the particular endpoint, the determination being made based on a measure of error for the decrypted symbol not exceeding a threshold error measure; and

in response to determining that the symbol was transmitted by the particular endpoint, logging the decrypted symbol as a valid symbol.

11 . A computer storage medium encoded with a computer program, the program comprising instructions that when executed by data processing apparatus cause the data processing apparatus to perform operations comprising:

receiving a symbol over a particular communications channel;

decrypting the symbol using a decryption key that is assigned to a particular endpoint that has been assigned to communicate over the particular communications channel;

determining that the symbol was transmitted by the particular endpoint, the determination being made based on a measure of error for the decrypted symbol not exceeding a threshold error measure; and

in response to determining that the symbol was transmitted by the particular endpoint, logging the decrypted symbol as a valid symbol.

12 . A system comprising:

a set of endpoints in a communications network, each of the endpoints in the set being assigned a different communications channel over which the endpoint communicates;

a substation processing unit coupled to the set of endpoints, the substation processing unit including one or more processors configured to interact with the set of endpoints and further configured to:

receive a symbol over a particular communications channel;

decrypt the symbol using a decryption key that is assigned to a particular endpoint that has been assigned to communicate over the particular communications channel;

determine that the symbol was transmitted by the particular endpoint, the determination being made based on a measure of error for the decrypted symbol not exceeding a threshold error measure; and

in response to determining that the symbol was transmitted by the particular endpoint, logging the decrypted symbol as a valid symbol.

13 . A system comprising:

a set of endpoints in a communications network, each of the endpoints in the set being assigned a different communications channel over which the endpoint communicates;

a substation processing unit coupled to the set of endpoints, the substation processing unit including one or more processors configured to interact with the set of endpoints and further configured to:

receive a symbol over a particular communications channel;

decrypt the symbol using a decryption key that is assigned to a particular endpoint that is assigned the particular communications channel;

compute a measure of error for the decrypted symbol;

determine whether the measure of error exceeds a threshold error measure;

in response to determining that the measure of error exceeds the threshold error measure, identify the decrypted symbol as a symbol from a different endpoint; and

in response to determining that the measure of error does not exceed the threshold error measure:

identify the decrypted symbol as a valid symbol transmitted by the particular endpoint; and

log the valid symbol.

14 . The system of claim 13 , wherein at least one of the endpoints is further configured to:

generate the symbol to include payload data and error correction data;

encrypt the symbol using an encryption key that is assigned to the particular endpoint; and

transmit the encrypted symbol over the particular communications channel.

15 . The system of claim 14 , wherein the at least one endpoint is further configured to:

insert an error correcting code into the payload data; and

encrypt the symbol following insertion of the error correcting code.

16 . The system of claim 13 , wherein the substation processing unit is further configured to:

receive a plurality of different symbols over a plurality of different communications channels, each different communications channel being assigned to a different endpoint; and

for each of the different communications channels, decrypt the symbol received over the communications channel using a decryption key that is assigned to the endpoint to which the communications channel is assigned.

17 . The system of claim 16 , wherein the substation processing unit is further configured to retrieve, for each different endpoint, a different decryption key that is assigned to the different endpoint.

18 . The system of claim 13 , wherein the substation processing unit is further configured to:

compute a bit error rate for the decrypted symbol; and

determine whether the bit error rate exceeds a threshold bit error rate.

19 . The system of claim 13 , wherein the set of endpoints are a set of meters in a power line communications network.

20 . The system of claim 13 , wherein the substation processing unit is further configured to iteratively decrypt the received symbol using different decryption keys and determine that the symbol is from a particular endpoint based on the decryption key for which the decrypted symbol has a lowest measure of error for the symbol.