What is claimed is:
1. A public key validation agent (PKVA) comprising:
an off-line registration authority for issuing a first unsigned public key validation certificate (unsigned PKVC) off-line to a subject that binds a public key of the subject to a first public key serial number (PKVN), the registration authority maintaining a certificate database of unsigned PKVCs in which it stores the first unsigned PKVC; and
an on-line credentials server for issuing a disposable public key validation certificate (disposable PKVC) on-line to the subject, the disposable PKVC binds the public key of the subject from the first unsigned PKVC to the first PKVN from the first unsigned PKVC, wherein the credentials server maintains a table that contains entries corresponding to valid unsigned PKVCs stored in the certificate database.
2. The PKVA of claim 1 wherein the first PKVN is different than all previous PKVNs generated by the registration authority.
3. The PKVA of claim 1 wherein the credentials server is responsive to a revocation request from the subject to invalidate the first unsigned PKVC entry in the table of the credential server.
4. The PKVA of claim 3 wherein the registration authority generates a public key revocation code (PKRC) to be used by the subject in its revocation request.
5. The PKVA of claim 4 wherein the registration authority sends the PKRC to the subject over a secure channel that provides data confidentiality.
6. The PKVA of claim 1 wherein the disposable PKVC includes an expiration datetime.
7. The PKVA of claim 6 wherein a validity period from when the credentials server issues the disposable PKVC to the expiration datetime is sufficiently short such that the disposable PKVC does not need to be subject to revocation.
8. The PKVA of claim 6 wherein the disposable PKVC is not subject to revocation.
9. The PKVA of claim 1 wherein the table maintained by the credentials server is a hash table containing cryptographic hashes of valid unsigned PKVCs stored in the certificate database and including a cryptographic hash of the first unsigned PKVC.
10. The PKVA of claim 1 wherein the credential server issues the disposable PKVC in response to a message from the subject containing the issued first unsigned certificate.
11. The PKVA of claim 9 wherein the credentials server computes the cryptographic hash of the first unsigned PKVC with a collision-resistant hash function.
12. The PKVC of claim 11 wherein the collision-resistant hash function is a SHA-1 hash function.
13. The PKVC of claim 11 wherein the collision-resistant hash function is a MD5 hash function.
14. The PKVC of claim 1 wherein the disposable PKVC permits the subject to present the disposable PKVC to a verifier for authentication and for demonstrating that the subject has knowledge of a private key corresponding to the public key in the disposable PKVC.
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 mesostructured aluminosilicate material consisting of at least two elementary spherical particles, each one of said spherical particles consisting essentially of a mesostructured matrix based on silicon oxide and aluminium oxide, said mesostructured matrix having a pore diameter ranging between 1.5 and 30 nm, a SiAl molar ratio at least equal to 1 and amorphous walls of thickness ranging between 1 and 30 nm, said elementary spherical particles having a diameter D greater than 10 \u03bcm and less than or equal to 100 \u03bcm.
2. A material as claimed in claim 1, such that said elementary spherical particles have a diameter D ranging between 11 and 70 \u03bcm.
3. A material as claimed in claim 2, such that said elementary spherical particles have a diameter D ranging between 11 and 50 \u03bcm.
4. A material as claimed in claim 3, such that said elementary spherical particles have a diameter D ranging between 15 and 50 \u03bcm.
5. A material as claimed in claim 1, such that the SiAl molar ratio of said mesostructured matrix ranges between 1 and 10.
6. A material as claimed in claim 5, such that the SiAl molar ratio of said mesostructured matrix ranges between 1 and 5.
7. A material as claimed in claim 1, such that the pore diameter of said matrix ranges between 1.5 and 10 nm.
8. A material as claimed in claim 1, having a specific surface area ranging between 200 and 1200 m2g.
9. A material as claimed in claim 8, having a specific surface area ranging between 300 and 1000 m2g.
10. A material as claimed in claim 1, such that said matrix based on silicon oxide and aluminium oxide has a hexagonal, vermicular, or cubic structure.
11. A method of preparing a mesostructured aluminosilicate material according to claim 1, comprising: a) mixing into a solution at least one surfactant, at least one aluminic precursor and at least one silicic precursor;
b) aerosol atomizing the solution obtained in stage a) using a spray nozzle that leads to the formation of liquid droplets of diameter less than or equal to 300 \u03bcm; c) drying said droplets; d) crushing the solid product obtained in stage c); e) mixing into a solution at least one surfactant, at least one aluminic precursor, at least one silicic precursor and at least a fraction of the solid product obtained in stage d); f) aerosol atomizing the suspension obtained in stage e) using a spray nozzle that leads to the formation of suspended droplets, which are precursors of the constituent spherical elementary particles of diameter D such that 10<D (\u03bcm)\u2266100 of the material; g) drying said droplets obtained in stage f); and h) removing said surfactant introduced in stages a) and e) so as to obtain a mesostructured porosity material.
12. A preparation method as claimed in claim 11, such that the volume percentage of non-volatile compounds present in the suspension according to said stage e) is at least 7%.
13. A method of preparing a mesostructured aluminosilicate material according to claim 8, comprising: a) mixing into a solution at least one surfactant, at least one aluminic precursor and at least one silicic precursor;
b) aerosol atomizing the solution obtained in stage a) using a spray nozzle that leads to the formation of liquid droplets of diameter less than or equal to 300 \u03bcm; c) drying said droplets;
and h) removing said surfactant so as to obtain a mesostructured porosity material.
14. A preparation method as claimed in claim 13, such that the volume percentage of non-volatile compounds present in the solution according to said stage a) is at least 7%.
15. An adsorbent comprising the mesostructured aluminosilicate material as claimed in claim 1.
16. A catalyst comprising the mesostructured aluminosilicate material as claimed in claim 1.