1. A compound semiconductor light-emitting device comprising:
a substrate having an upper surface, a lower surface, and a plurality of device side surfaces; and
a light-emitting layer grown on the upper surface of said substrate,
wherein at least one of the device side surfaces has an array of recessed portions, individual ones of the recessed portions extend from the lower surface to the upper surface of the substrate, and individual ones of the recessed portions have a semi-circular shape in cross section parallel to the upper surface of the substrate, and
wherein the depth of individual ones of the recessed portions is a radius of the semi-circular shape in a direction parallel to the upper surface of the substrate, and the height of individual ones of the recessed portions from the lower surface to the upper surface of the substrate is at least 20 \u03bcm, and wherein a distance of 4 to 40 \u03bcm is maintained between adjacent recessed portions in the array of the recessed portions.
2. A light-emitting device according to claim 1, wherein the light-emitting layer comprises an n-type or p-type compound semiconductor and is of the pn junction type.
3. A light-emitting device according to claim 1, wherein the substrate is selected from the group consisting of a sapphire, a SiC and a III-V Group compound semiconductor single crystal.
4. A light-emitting device according to claim 1, wherein the depth of individual ones of the recessed portions is 0.5 to 10 \u03bcm.
5. A light-emitting device according to claim 1, wherein the compound semiconductor light-emitting device is of the flip-chip type.
6. A lamp comprising a compound semiconductor light-emitting device of claim 1.
7. A source of light comprising a lamp of claim 6.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of authenticating an object using a processor, the method including steps of:
receiving indicating data, the indicating data being generated in response to sensing of coded data provided on or in a surface associated with the object, the indicating data being indicative of:
an identity; and,
a part of a signature, the signature being a digital signature of at least a part of the identity and at least part of predetermined padding, and comprising a plurality of signature parts;
determining from the indicating data, a received identity, a received signature part and a received signature part identifier;
determining, using the received identity and the received signature part identifier, a determined signature part;
comparing the determined signature part to the received signature part; and
authenticating the object using the result of the comparison,
wherein the step of determining the determined signature part comprises sub-steps of:
determining, using the received identity, the predetermined padding;
determining, using the predetermined padding, the received identity, and a secret key, the determined signature; and
determining the determined signature part from the determined signature and the received signature part identifier.
2. A method according to claim 1, wherein the method includes further steps of:
generating authentication data indicative of success or failure of the authentication; and
transferring the authentication data to a user.
3. A method according to claim 2, wherein the method further includes a step of transferring the authentication data to a sensing device.
4. A method according to claim 1, wherein the processor forms part of a sensing device, and wherein the indicating data is received from a sensor in the sensing device.
5. A method according to claim 1, wherein the processor communicates with a sensing device which generates the indicating data, and wherein the indicating data is received from the sensing device.
6. A method according to claim 5, wherein the method includes, in the processor, communicating with the sensing device via at least one of:
a communications network;
the Internet;
a mobile phone network; and,
a wireless connection.
7. A method according to claim 1, wherein the indicating data is further indicative of at least one of:
a location of the respective data portion;
a position of the respective data portion on the surface;
a size of the data portions;
a size of the signature;
a size of the signature part;
an identity of a signature part;
units of indicated locations;
redundant data;
data allowing error correction;
Reed-Solomon data; and,
Cyclic Redundancy Check (CRC) data.
8. A method according to claim 1, wherein the digital signature includes at least one of:
a random number associated with the identity;
a keyed hash of at least the identity;
a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key;
cipher-text produced by encrypting at least the identity;
cipher-text produced by encrypting at least the identity and a random number; and,
cipher-text produced using a private key, and verifiable using a corresponding public key.
9. A method according to claim 1, wherein the identity includes the identity of at least one of:
the object;
the surface; and
a region of the surface.
10. A method according to claim 1, wherein the identity includes at least one of:
an Electronic Product Code (EPC);
a National Drug Code (NDC) number;
a serial number of a pharmaceutical item;
a currency note attribute including at least one of:
currency;
issue country;
denomination;
note side;
printing works; and
serial number;
a check attribute including at least one of:
currency;
issuing institution;
account number;
serial number;
expiry date;
check value; and
limit; and
a card attribute including at least one of:
card type;
issuing institution;
account number;
issue date;
expiry date; and
limit.
11. A method according to claim 1, wherein the processor determines the determined signature part by sub-steps of:
communicating to a second processor the received identity, the second processor generating the determined signature using the received identity and a secret key
receiving from the second processor the determined signature; and
determining the determined signature part from the determined signature and the received signature part identifier.
12. A method according to claim 1, wherein the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.
13. A method according to claim 1, wherein the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.
14. A processor for authenticating an object, the object being associated with a surface having disposed thereon or therein coded data indicative of:
an identity of the object; and
parts of a signature, the signature being a digital signature of at least a part of the identity and at least part of predetermined padding, and comprising a plurality of signature parts,
the processor comprising:
means for receiving indicating data, the indicating data being generated in response to sensing at least part of the coded data, the indicating data being indicative of the identity and one part of the signature;
means for determining, using the indicating data, a determined identity, the part of the signature, and a signature part identifier;
means for generating, using the determined identity and the signature part identifier, a determined signature part by:
determining, using the received identity, the predetermined padding;
determining, using the predetermined padding, the received identity, and secret key, the determined signature; and
determining the determined signature part from the determined signature and the received signature part identifier;
means for comparing the determined signature part to the one part of the signature; and
means for authenticating the object using the result of the comparison.