go/crypto RSA key validation

gistfile1.md

Current version (20 iterations of ProbablyPrime):

$ go test -run none -bench=. -benchtime=60s
PASS
BenchmarkRSA2048Validate	    1000	 137668985 ns/op
...

Fewer (2) iterations of ProbablyPrime:

$ go test -run none -bench=. -benchtime=15s
PASS
BenchmarkRSA2048Validate	    2000	  14034241 ns/op
...

Dropping the ProbablyPrime check entirely:

$ go test -run none -bench=. -benchtime=1s
PASS
BenchmarkRSA2048Validate	  200000	      7835 ns/op
...

The benchmark code (key lifted from neighboring BenchmarkRSA2048Decrypt):

func BenchmarkRSA2048Validate(b *testing.B) {
    b.StopTimer()
    priv := &PrivateKey{
        PublicKey: PublicKey{
            N: fromBase10("14314132931241006650998084889274020608918049032671858325988396851334124245188214251956198731333464217832226406088020736932173064754214329009979944037640912127943488972644697423190955557435910767690712778463524983667852819010259499695177313115447116110358524558307947613422897787329221478860907963827160223559690523660574329011927531289655711860504630573766609239332569210831325633840174683944553667352219670930408593321661375473885147973879086994006440025257225431977751512374815915392249179976902953721486040787792801849818254465486633791826766873076617116727073077821584676715609985777563958286637185868165868520557"),
            E: 3,
        },
        D: fromBase10("9542755287494004433998723259516013739278699355114572217325597900889416163458809501304132487555642811888150937392013824621448709836142886006653296025093941418628992648429798282127303704957273845127141852309016655778568546006839666463451542076964744073572349705538631742281931858219480985907271975884773482372966847639853897890615456605598071088189838676728836833012254065983259638538107719766738032720239892094196108713378822882383694456030043492571063441943847195939549773271694647657549658603365629458610273821292232646334717612674519997533901052790334279661754176490593041941863932308687197618671528035670452762731"),
        Primes: []*big.Int{
            fromBase10("130903255182996722426771613606077755295583329135067340152947172868415809027537376306193179624298874215608270802054347609836776473930072411958753044562214537013874103802006369634761074377213995983876788718033850153719421695468704276694983032644416930879093914927146648402139231293035971427838068945045019075433"),
            fromBase10("109348945610485453577574767652527472924289229538286649661240938988020367005475727988253438647560958573506159449538793540472829815903949343191091817779240101054552748665267574271163617694640513549693841337820602726596756351006149518830932261246698766355347898158548465400674856021497190430791824869615170301029"),
        },
    }
    b.StartTimer()
    for i := 0; i < b.N; i++ {
        priv.Validate()
    }
}