Single-Ended and Differential S-Parameters
Differential circuits have been important incommunication systems for many years. In the past,differential communication circuits operated at lowfrequencies, where they could be designed andanalyzed using lumped-element models andtechniques. With the frequency of operationincreasing beyond 1GHz, and above 1Gbps fordigital communications, this lumped-elementapproach is no longer valid, because the physicalsize of the circuit approaches the size of awavelength.Distributed models and analysis techniques are nowused instead of lumped-element techniques.Scattering parameters, or S-parameters, have beendeveloped for this purpose [1]. These S-parametersare defined for single-ended networks. S-parameterscan be used to describe differential networks, but astrict definition was not developed until Bockelmanand others addressed this issue [2]. Bockelman’swork also included a study on how to adapt single-ended S-parameters for use with differential circuits[2]. This adaptation, called “mixed-mode S-parameters,” addresses differential and common-mode operation, as well as the conversion betweenthe two modes of operation.This application note will explain the use of single-ended and mixed-mode S-parameters, and the basicconcepts of microwave measurement calibration.
標(biāo)簽：
差分電路
單端
模式
上傳時間：
2014-03-25
上傳用戶：yyyyyyyyyy
Digital Signature Algorithm (DSA)是Schnorr和ElGamal簽名算法的變種，被美國NIST作為DSS(DigitalSignature Standard)。算法中應(yīng)用了下述參數(shù)：
p：L bits長的素數(shù)。L是64的倍數(shù)，范圍是512到1024；
q：p - 1的160bits的素因子；
g：g = h^((p-1)/q) mod p，h滿足h < p - 1, h^((p-1)/q) mod p > 1；
x：x < q，x為私鑰 ；
y：y = g^x mod p ，( p, q, g, y )為公鑰；
H( x )：One-Way Hash函數(shù)。DSS中選用SHA( Secure Hash Algorithm )。
p, q, g可由一組用戶共享，但在實際應(yīng)用中，使用公共模數(shù)可能會帶來一定的威脅。簽名及驗證協(xié)議如下：
1. P產(chǎn)生隨機數(shù)k，k < q；
2. P計算 r = ( g^k mod p ) mod q
s = ( k^(-1) (H(m) + xr)) mod q
簽名結(jié)果是( m, r, s )。
3. 驗證時計算 w = s^(-1)mod q
u1 = ( H( m ) * w ) mod q
u2 = ( r * w ) mod q
v = (( g^u1 * y^u2 ) mod p ) mod q
若v = r，則認為簽名有效。
DSA是基于整數(shù)有限域離散對數(shù)難題的，其安全性與RSA相比差不多。DSA的一個重要特點是兩個素數(shù)公開，這樣，當(dāng)使用別人的p和q時，即使不知道私鑰，你也能確認它們是否是隨機產(chǎn)生的，還是作了手腳。RSA算法卻作不到。
標(biāo)簽：
Algorithm
Signature
Digital
Schnorr
上傳時間：
2014-01-01
上傳用戶：qq521
