Commitment schemes Sample Clauses

Commitment schemes. An important cryptographic building block we will be using in our protocol is message commitment. The rea- son we use commitments is because we want to impose the following restrictions on our users: (i) a user who commits to a certain value (a DH public key in our case) cannot change this value afterwards (the scheme is binding ); (ii) the commitment is hidden from its re- ceiver until the sender “opens” it (the scheme is hiding ). A commitment scheme transforms a value m into a com- mitment/opening pair (c, d), where c reveals no infor- mation about m, but (c, d) together reveal m, and it is DH Abbr.“Xxxxxx-Xxxxxxx” ⊕ Bitwise “xor” operation (system parameter) g A generator of Z∗, (2 ≤ g ≤ p − 2) (system parameter) (c, d) ← Commit(m) The commitment/open- ing pair (c, d) for m ' m ← Open(c, d) Opens the commitment κ A security parameter in our protocol (κ ∈ N) M The set of |M | distinct items (e.g., words), s.t. |M |κ |Z∗| infeasible to find d ' ' such that (c, d ) reveals m /= m. Now, if A wants to commit a value m to B, she first generates the commitment/openeing pair (cA, dA) ← Commit(m), and sends cA to B. To open m, A simply We first describe a basic protocol with a general com- mitment scheme. The employed commitment scheme should exhibit the following properties: (i) it should be sends d A to B, who runs m ← Open(cA, dA). If the perfect-hiding; (ii) it should be computationally bind- ' employed commitment scheme is “correct”, at the end of the protocol we must have m = m. In this paper we will make use of a collision-free hash function based commitment scheme due Halevi and Mi- cali [13]. We call this scheme the Xxxxxx-Xxxxxx com- mitment scheme [13]. This scheme is a very practical commitment scheme based solely on collision-free hash- ing. To commit to a message M , the sender picks at random a string x and a universal hash function f so that f (x) = M . Then the user applies the collision-free hash function h (e.g. SHA-1, which is believed to be collision free) to the random string x to get y = h(x) and sends the commit string c = (y, f ) to the intended receiver. To open the commit string, the sender simply sends the random string x. The efficiency of this com- mitment scheme comes from the fact that it makes use ing [13]. We emphasize here that computationally- hiding and perfect-binding schemes would work as well. However, for the clarity of the presentation we restrict ourselves, without any loss of generality, to the first type of commitmen...
Sample 1

Related to Commitment schemes

  • L/C Commitment (a) Subject to the terms and conditions hereof, the Issuing Lender, in reliance on the agreements of the other Lenders set forth in Section 3.4(a), agrees to issue letters of credit (“Letters of Credit”) for the account of the Borrower on any Business Day during the Revolving Commitment Period in such form as may be approved from time to time by the Issuing Lender; provided that the Issuing Lender shall have no obligation to issue any Letter of Credit if, after giving effect to such issuance, (i) the L/C Obligations would exceed the L/C Commitment or (ii) the aggregate amount of the Available Revolving Commitments would be less than zero. Each Letter of Credit shall (i) be denominated in Dollars and (ii) expire no later than the earlier of (x) the first anniversary of its date of issuance and (y) the date that is five (5) Business Days prior to the Revolving Termination Date, provided that any Letter of Credit with a one-year term may provide for the renewal thereof for additional one-year periods (which shall in no event extend beyond the date referred to in clause (y) above). (b) The Issuing Lender shall not at any time be obligated to issue any Letter of Credit if (i) such issuance would conflict with, or cause the Issuing Lender or any L/C Participant to exceed any limits imposed by, any applicable Requirement of Law or (ii) any Lender is at that time a Defaulting Lender, unless the Issuing Lender has entered into arrangements, including the delivery of Cash Collateral, satisfactory to the Issuing Lender (in its sole discretion) with the Borrower or such Lender to eliminate the Issuing Lender’s actual or potential Fronting Exposure (after giving effect to Section 2.23(a)(iv)) with respect to the Defaulting Lender arising from either the Letter of Credit then proposed to be issued or that Letter of Credit and all other L/C Obligations as to which the Issuing Lender has actual or potential Fronting Exposure, as it may elect in its sole discretion.

  • Term Commitment Subject to the terms and conditions of this Agreement, Bank hereby agrees to make advances to Borrower from time to time up to and including October 1, 2001, not to exceed the aggregate principal amount of One Million Two Hundred Thousand Dollars ($1,200,000.00) ("Term Commitment"), the proceeds of which shall be used to finance Borrower's capital expenditures, and which shall be converted on October 1, 2001, to a term loan, as described more fully below. Borrower's obligation to repay advances under the Term Commitment shall be evidenced by a promissory note substantially in the form of Exhibit D attached hereto ("Term Commitment Note"), all terms of which are incorporated herein by this reference.

  • Additional Commitments The Parties may negotiate commitments with respect to measures affecting trade in services not subject to scheduling under Article 106 (National Treatment) or Article 107 (Market Access), including those regarding qualifications, standards or licensing matters. Such commitments shall be inscribed in a Party's Schedule.

  • STAFF COMMITMENT If this Settlement Agreement is accepted by the Hearing Panel, Staff will not initiate any proceeding under the By-laws of the MFDA against the Respondent in respect of the facts set out in Part IV and the contraventions described in Part V of this Settlement Agreement, subject to the provisions of Part IX below. Nothing in this Settlement Agreement precludes Staff from investigating or initiating proceedings in respect of any facts and contraventions that are not set out in Parts IV and V of this Settlement Agreement or in respect of conduct that occurred outside the specified date ranges of the facts and contraventions set out in Parts IV and V, whether known or unknown at the time of settlement. Furthermore, nothing in this Settlement Agreement shall relieve the Respondent from fulfilling any continuing regulatory obligations.

  • Term Commitments Subject to the terms and conditions hereof, each Term Lender severally agrees to make a term loan (a “Term Loan”) to the Borrower on the Closing Date in an amount not to exceed the amount of the Term Commitment of such Lender. The Term Loans may from time to time be Eurodollar Loans or ABR Loans, as determined by the Borrower and notified to the Administrative Agent in accordance with Sections 2.2 and 2.12.

  • Investment Commitment The undersigned's overall commitment to investments which are not readily marketable is not disproportionate to the undersigned's net worth, and an investment in the Shares will not cause such overall commitment to become excessive.

  • Commitment Within 20 days after the Title Company receives a copy of this contract, Seller shall furnish to Buyer a commitment for title insurance (Commitment) and, at Buyer's expense, legible copies of restrictive covenants and documents evidencing exceptions in the Commitment (Exception Documents) other than the standard printed exceptions. Seller authorizes the Title Company to deliver the Commitment and Exception Documents to Buyer at Buyer's address shown in Paragraph 21. If the Commitment and Exception Documents are not delivered to Buyer within the specified time, the time for delivery will be automatically extended up to 15 days or 3 days before the Closing Date, whichever is earlier. If the Commitment and Exception Documents are not delivered within the time required, Buyer may terminate this contract and the xxxxxxx money will be refunded to Buyer.

  • The Commitment Subject to the terms and conditions of this Agreement, Lender agrees to make term loans to Borrower from time to time from the Closing Date and to, but not including, the Termination Date in an aggregate principal amount not exceeding the Commitment. The Commitment is not a revolving credit commitment, and Borrower does not have the right to repay and reborrow hereunder. Each Loan requested by Borrower to be made on a single Business Day shall be for a minimum principal amount set forth in the Supplement, except to the extent the remaining Commitment is a lesser amount.

  • Term Loan Commitment As to each Term Loan Lender, the amount equal to such Term Loan Lender’s Term Loan Commitment Percentage of the aggregate principal amount of the Term Loans from time to time outstanding to the Borrower.

  • Additional Commitment Lenders The Company shall have the right, but shall not be obligated, on or before the applicable Maturity Date for any Non-Extending Lender to replace such Non-Extending Lender with, and add as “Lenders” under this Agreement in place thereof, one or more financial institutions that are not Ineligible Institutions (each, an “Additional Commitment Lender”) approved by the Administrative Agent in accordance with the procedures provided in Section 2.19(b), each of which Additional Commitment Lenders shall have entered into an Assignment and Assumption (in accordance with and subject to the restrictions contained in Section 9.04, with the Company or replacement Lender obligated to pay any applicable processing or recordation fee) with such Non-Extending Lender, pursuant to which such Additional Commitment Lenders shall, effective on or before the applicable Maturity Date for such Non-Extending Lender, assume a Commitment (and, if any such Additional Commitment Lender is already a Lender, its Commitment shall be in addition to such Lender’s Commitment hereunder on such date). Prior to any Non-Extending Lender being replaced by one or more Additional Commitment Lenders pursuant hereto, such Non-Extending Lender may elect, in its sole discretion, by giving irrevocable notice thereof to the Administrative Agent and the Company (which notice shall set forth such Lender’s new Maturity Date), to become an Extending Lender. The Administrative Agent may effect such amendments to this Agreement as are reasonably necessary to provide for any such extensions with the consent of the Company but without the consent of any other Lenders.