1. A cryptographic method during which an integer division of the type q=a div b and r=a mod b is performed, where q is a quotient, a is a number containing m bits, b is a number of containing n bits, with n less than or equal to m and bn\u22121 is non-zero, bn\u22121 being the most significant bit of b, comprising the following steps:
(i) performing a partial division of a word A, comprising of n bits of the number a, by the number b to obtain a bit of the quotient q, wherein at least one of the numbers a and b comprises secret data;
(ii) repeating step (i) for m\u2212n+1 iterations with the same operations being performed at each iteration, regardless of the value of the quotient bit obtained, to obtain the quotient q; and
(iii) generating encrypted or decrypted data in accordance with said quotient.
2. A method according to claim 1, wherein, at each iteration, an addition of the number b to the word A and a subtraction of the number b from the word A are performed.
3. A method according to claim 1, wherein all the following steps are performed:
Input: a=(0, an\u22121, . . . , a0)
b=(bn\u22121, . . . , b0)
Output: q=a div b and r=a mod b
A=(0, am\u22121, . . . , am\u2212n+1); \u03c3\u2032\u21901
For j=1 to (m\u2212n+1), do:
a\u2190SHLm+1(a, 1); \u03c3\u2190carry
A\u2190(\u03c3\u2032)SUBn(A, b)+(\u03c3)ADDn(A, b)
\u03c3\u2190(\u03c3\u2032 AND \u03c3\u2032)(\u03c3\u2032 AND carry)(\u03c3\u2032 AND carry)
lsb(a) \u03c3\u2032
\u03c3\u2032\u2190\u03c3
End For
if (\u03c3=TRUE) then A\u2190ADDn(A, b)
4. A method according to claim 1 wherein, at each iteration, either the number b or of a number {overscore (b)} complementary to the number b is added to the word A.
5. A method according to claim 4, further including the step, at each iteration, of updating a first variable (\u03c3\u2032) indicating whether, during the following iteration, the number b or the number {overscore (b)} is to be added with the word A according to the quotient bit produced.
6. A method according to claim 4, during wherein all the following steps are performed:
Input: a=(0, am\u22121, . . . , a0)
b=(bn\u22121, . . . , b0)
Output: q=a div b and r=a mod b
A=(0, am\u22121, . . . , am\u2212n+1); \u03c3\u2032\u21901; {overscore (b)}\u2190CPL2N(b)
For j=1 to (m\u2212n+1), do:
a\u2190SHLm+1(a, 1); \u03c3\u2190carry
daddr\u2190baddr+\u03c3\u2032({overscore (b)}addr\u2212baddr)
A\u2190ADDn(A, d)
\u03c3\u2190(\u03c3\u2032 AND \u03c3\u2032)(\u03c3\u2032 AND carry)(\u03c3\u2032 AND carry)
lsb(a)\u2190\u03c3\u2032
\u03c3\u2032\u2190\u03c3
End For
if (\u03c3=TRUE) then A\u2190ADDn(A, b)
7. A method according to claim 1, further including the steps, at each iteration, of performing an operation of complement to 2n of an updated data item (b or {overscore (b)}) or of a notional data item (c or {overscore (c)}), and adding the updated data item with the word A.
8. A method according to claim 7, further including the step, at each iteration, of updating a second variable (\u03b4), indicating whether, during the following iteration, the operation of complement to 2n is to be performed on the updated data item or on the notional data item.
9. A method according to claim 7, further including the step, at each iteration, of updating of a third variable (\u03b2) indicating whether the updated data item is equal to the data item b or to its complement to 2n.
10. A method according to claim 7, wherein all the following steps are also performed:
Input: a=(0, am\u22121, . . . , a0)
b=(bn\u22121, . . . , b0)
Output: q=a div b and r=a mod b
\u03c3\u2032\u21901; \u03b2\u21901, \u03b3\u21901; A=(0, am\u22121, . . . , am\u2212n+1)
for j=1 to (m\u2212n+1), do:
a\u2190SHLm+1(a, 1); \u03c3\u2190carry
\u03b4\u2190\u03c3\u2032\u03b2
daddr\u2190baddr+\u03b4(caddr\u2212baddr)
d\u2190CPL2n(d)
A\u2190ADDn(A, b)
\u03c3\u2190(\u03c3 AND \u03c3\u2032)(\u03c3 AND carry)(\u03c3\u2032 AND carry)
\u03b2\u2190\u03c3\u2032; \u03b3\u2190\u03b3\u03b4; \u03c3\u2032\u2190\u03c3
lsb(a)=\u03c3
end for
if (\u03c3=TRUE) then A\u2190ADDn(A, b)
11. A method according to claim 10, at the end, the following operations are performed:
if (\u03b2=TRUE) then b\u2190CPL2n(b)
if (\u03b3=TRUE) then c\u2190CPL2n(c).
12. An electronic component comprising calculation means programmed to implement a method according to claim 1, said calculation means comprising a central unit associated with a memory comprising several registers for storing the data a and b.
13. A chip card comprising an electronic component according to claim 12.
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. An optical pickup comprising:
an objective lens;
a protection member for protecting the objective lens; and
a lens holding member configured to hold the objective lens and the protection member,
wherein the protection member includes (i) a bearing surface configured to contact a surface of an edge portion of the objective lens not facing an optical recording medium, (ii) an aperture configured to control a diameter of laser light to be incident on the objective lens, and (iii) a protection portion protruding toward the optical recording medium with respect to the objective lens, in which the bearing surface, the aperture, and the protection portion are integrally formed with one another.
2. The optical pickup according to claim 1, wherein the lens holding member includes a bonding recess configured to bond the objective lens and the protection member with the lens holding member.
3. The optical pickup according to claim 2, wherein the protection member includes a cut portion configured to bond the objective lens with an adhesive filled in the bonding recess.
4. The optical pickup according to claim 1, wherein the lens holding member includes a fitting portion configured to position the protection member.
5. The optical pickup according to claim 1, wherein the protection member includes a fitting portion configured to position the objective lens, the fitting portion having the bearing surface.
6. The optical pickup according to claim 1, wherein the lens holding member includes a fitting portion configured to position the objective lens.
7. An optical disk drive apparatus configured to rotationally drive an optical recording medium, to condense laser light onto the optical recording medium, and to effect at least one of reproducing and recording of an information signal from andor on the optical recording medium with reflection light of the laser light, said optical disk drive apparatus comprising:
an objective lens;
a protection member for protecting the objective lens; and
a lens holding member configured to hold the objective lens and the protection member,
wherein the protection member includes (i) a bearing surface configured to contact a surface of an edge portion of the objective lens not facing an optical recording medium, (ii) an aperture configured to control a diameter of laser light to be incident on the objective lens, and (iii) a protection portion protruding toward the optical recording medium with respect to the objective lens, in which the bearing surface, the aperture, and the protection portion are integrally formed with one another.
8. The optical disk drive apparatus according to claim 7, wherein the lens holding member includes a bonding recess configured to bond the objective lens and the protection member with the lens holding member.
9. The optical disk drive apparatus according to claim 8, wherein the protection member includes a cut portion configured to bond the objective lens with an adhesive filled in the bonding recess.
10. The optical disk drive apparatus according to claim 7, wherein the lens holding member includes a fitting portion configured to position the protection member.
11. The optical disk drive apparatus according to claim 7, wherein the protection member includes a fitting portion configured to position the objective lens, the fitting portion having the bearing surface.
12. The optical disk drive apparatus according to claim 7, wherein the lens holding member includes a fitting portion configured to position the objective lens.