About Guido Maria Serra aka Zeph

Sviluppatore, sistemista, analista di sicurezza, freesoftware evangelist.

is the Galaxy S6 Edge the only LTE phone for US/EU travellers?

I mean, I live in Germany, but I work for an american company based in Orange County (Southern California, USA) and Verizon seems to be the king over there as the CDMA technology allows them to cover 10 times the range of what a GSM tower can cover. Verizon is NO option for a european like me as to have their simcard you need to have a phone that they purchased in batches and registered in their infrastructure. You cannot bring in your own phone, even if the tech specs of the phone are fine. You simply can’t. Well, they won’t you let BYOD (bring your own device). Unless it is an iPhone 6s [probably Apple forced them to preemptively register all their IMEIs in the network]


If you are living in Germany, you do need a phone that has the LTE FDD frequencies 3,7 and 20 (in MHz 1800, 2600 and 800) according to https://en.wikipedia.org/wiki/List_of_LTE_networks_in_Europe

If you live in Italy, same set of frequencies.

If you wanna travel to US, and don’t wanna have to purchase a phone from Verizon (it will take you at least 6 months of contract with them to get it unlocked… so, until you can put in your italian/german simcard) you have to go for T-Mobile. Therefore… frequencies LTE FDD 2,4 and 12 (again in MHz 1900, 1700 and 700a -> no clue what’s the “a” stands for) Check https://en.wikipedia.org/wiki/List_of_LTE_networks#Americas for further details.

Well… the only phone that has LTE FDD frequencies 2,3,4,7,12,20 all in one, is the Samsung S6 EDGE -> http://www.samsung.com/us/explore/galaxy-s-6-features-and-specs/

It also has at least one match for Docomo (Japanese carriere) required frequencies: LTE FDD 1 (2100 MHz) … forget about the others: 9(3), 19(5,26) and 28. It was already a miracle for me to put my hands on a prepaid “data only” simcard while in Tokyo on spring last year. Apparently you cannot have a “voice” simcard unless you are a resident…

Has anybody else found another phone suitable for a “global traveller”? Possibly cheaper than the S6 😉 …and maybe dual-sim too… k, now I’m asking too much I guess. 😀

UPDATE: [strike out 1] The Nexus 5X as it has all the frequencies I need plus it is a an LTE Cat 6 phone [strike out 2] The Sony Xperia Z5 (it has also an internal microSD slot) The Motorola Moto X Style (more cost effective, and has up to 128Gb microSSD card slot) is most likely to be my next phone. Thanks to Fra Costa for introducing me to Project Fi (very cool indeed, but I’m not US based). Here is a list of all the other LTE Cat 6 devices…  (not only Cat6)




cervelli in fuga

(Copio e incollo dal post su facebook. Sono felice di aver fatto parte del progetto)
Aladino A. Amantini: Sono molto fiero di questo video. Quasi quanto lo sono dei miei amici

Con la partecipazione di (tra gli altri):

Se siete interessati a Sailing Film, il progetto di Jacopo: http://www.sailingfilm.com
Se siete interessati ai progetti tecnici di Renato: https://www.facebook.com/xevilstar
Se siete interessati a Gaia Italia, il progeto di Giacomo: http://www.acquarishop.it
Se siete interessati ad andare a lavorare in Olanda con Fernando e Andrea sentite me (da oggi cacciatore di teste)
Music Title: brain Author Frankie C
Licence: Creatice Commons 3.0 (Attribution – No Derivative Works)

Tassodi in località Corno a Predore

qualche giorno fa sono stato contattato su facebook da un amico di famiglia che mi segnalava uno scempio ai tassodi fatti piantare da mio nonno, il botanico Luigi Fenaroli, a protezione delle sponde del Lago d’Iseo

a differenza di mio nonno non so assolutamente nulla di piante, mi occupo di altro nella vita, ritengo pero’ che per quel che ho potuto vedere, per come stanno realizzando la pista ciclabile, si sta facendo qualcosa di buono per l’intera comunita’. E’ una bellissima rivalutazione delle nostre sponde e anche un esaltazione del lavoro di mio nonno. La ciclabile corre accanto ai tassodi in un’atmosfera molto romantica. Spero che a questi lavori segua anche un attivita’ di risanamento della ciclabile che prosegue lungo la strada costiera (chiusa al traffico e trasformata in pedonale) che vedete nelle mie foto qua sotto


… questa qui sotto e anche altre foto, sono solo per curiosita’ mia e/o per far vedere la bellezza del posto

caposaldo geodetico


















partially qualified domain names, OS X Yosemite v10.10.1

Apple broke DNS compatibility towards partially qualified domain names with the latest OS X release. On Nov. 18th they released an update with a patch to this issue (since I spent the time to escalate it). From http://support.apple.com/en-us/HT204017 release notes I quote:

Allows you to append search domains for partially qualified domain names when performing DNS lookups (consult the discoveryd man page for more information)

How was it supposed to work? And how can we activate it?

If you are a big corporation you are going to have a very complicate and hierarchically designed DNS system. Sometimes you just want to shorten the amount of data you type in to jump from one box to another, so… taking as a sample the Akamai mirror of apple.com you’ll see that will CNAME to e3191.dscc.akamaiedge.net. Imagine you are working for Akamai, and you need to ssh into e3191.dscc , without the partially qualified domain name feature you’ll have to type in the full fqdn. Instead, if you have akamaiedge.net in your domain search field, you don’t have to, your resolver will do it for you.

So, on OS X… I quote from my Apple Support guy’s email:

You can edit /System/Library/LaunchDaemons/com.apple.discoveryd.plist and add ‘–AlwaysAppendSearchDomains’ as a string to the ‘ProgramArguments’ array. That should re-enable search domains for PQDNs once you reboot after saving.

I add… you can simply “sudo launchctl unload /System/Library/LaunchDaemons/com.apple.discoveryd.plist” and “load” to refresh the daemon after having edited the file, without rebooting your laptop/workstation…

enjoy 😉

bullied by Tegel airport security

UPDATE 16/6/’14: I got a police letter today apologizing for the the behaviour of the airport personnel: “Ich möchte mich an dieser Stelle für das Verhalten der beiden Mitarbeiter entschuldigen und bedauere, dass Ihnen dadurch Unbehagen entstanden ist”.

Remains unclear the choice regarding the minced meat if it is a liquid or not, I left that to them to clarify as it is totally on a rule-of-thumb basis…. since the industry is putting a mark in milligrams on its plastic containers and not milliliters. THIS WAS IT> http://www.edeka-scharrer-shop.de/product/22715-Ruegenwalder_Muehle_Teewurst_fein_im_Becher_125_g

UPDATE 23/5/’14: A police representative wrote me back that they are investigating about the event and they’ll keep me posted as soon as they have gathered some facts about the incident.

UPDATE 15/5/’14: I got contacted on Monday, 12th May, by the person in charge of customer experience at the Berlin Airports. Seems that those guys are reporting directly to the border police officers. I’ll try to contact them

short-version of long story: I was travelling from TXL to MXP carrying 2 snacks of german teewurst (meat) to be spread on bread the guy at the security asked me to trash it, without thinking twice I went to the bin, which was full, so I left them on top of it

but then I realized that I was entitled to carry them, as a) they were not liquids, or at least their measurement on the box is obviously not in milliliters but in gramms… and b) even if they could argue it was a liquid thing, they definitely were under the 100ml each … so, I asked why I had to trash them > the same guy replied that I was not entitled, I argued instead that I was, he carried on… then at that point I asked to talk to his manager


his manager argued I couldn’t… then finally one of their colleagues pointed out they were not in a resealable-transparent-plastic-bag… they were instead in their plastic container, in a normal shopping plastic bag… I asked for one, but they refused me one… I then argued that they should have had them available, and the manager harshily replied that was not supposed to be the case… at that point I gave up and went to the gate

2nd attempt

I passed through the duty free area, and I asked to such a bag, I kindly got one, and I went back to the security to retrieve my goods > wrong, I was pushed back cause the bag was not transparent… gave up, went back to the gate, returning the bag at the duty free

3rd attempt

they guy at the duty free then kindly came back to me again, with a bag, with a zip, transparent… it was perfect… I went back to security > at this stage, with a big smile on their faces, the guys at the gate pointed out that _by_coincidence_ the cleaning guy passed by and pushed my goods inside the trash bin… so, if I wanted I could dig into it to retrieve it…


at that point I was out of myself… outraged, offended, humiliated, I asked the guy that had me trash them to provide his name; he refused the name, and had no identification sign on his clothes … I was almost missing my flight, I went back to the gate


at home, I wrote on Berlin Airport communication form, but as of now (3 days later, weekend has passed) I have no answer whatsover > I want to reach the HR department, walk over with a security officer to the gate and identify the guy: if anybody from Tegel airport is reading this, it was the security personnel, of a third party company, in charge at 18:15 (on Friday 9th May ’14) at the security screening towards gate C68

retweet me

further reading

offro lavoro

abbiamo budget per l’assunzione di 3 persone in Sony Playstation
datacenter engineer https://www.linkedin.com/jobs2/cap/view/13220463
sospesa sino ad agosto… per il momento non stiamo conducendo colloqui)
– network engineer https://www.linkedin.com/jobs2/view/13274419
– security engineer* https://www.linkedin.com/jobs2/view/10603940
* si, lo so che il job posting e’ per gli states, ma c’e’ la posizione gemella a Berlino

vi faccio io un prescreening in inglese via skype (il mio ID e’ zeph1ro, aggiungetemi),
non mandatemi curriculum in italiano perche’ finiranno direttamente nel cestino 😉
(si, ho scritto questo post in italiano per intercettare le vs ricerche su google)

p.s. lo aggiungo (non si sa mai), https://www.linkedin.com/jobs2/cap/view/12896708
posizione della madonna come *SENIOR* C++ developer, ma dovete avere il visto USA

bitcoin, versione breve

mi e’ stato chiesto di recente un tutorial sui bitcoins… non che abbia molto senso per uno che mastica la materia, visto che il paper scientifico dell’autore (Satoshi Nakamoto) e’ pubblico qui

cmq, eccovi la spiegazione spicciola…

Il tutto si basa sul costo computazionale di ottenere un particolare hash. Un hash e’ una serie di caratteri alfanumerici, rappresentante un numero, ottenuto dall’applicazione di una formula matematica. La piu’ semplice e conosciuta e’ l’operazione di modulo. Dividendo un numero per un altro, otteniamo un risultato. Questa operazione puo’ dare un risultato intero, o frazionario. Se ci limitiamo al risultato intero, avremo sicuramente un resto. L’operazione di modulo e’ una divisione da cui otteniamo solo il resto e non il valore della divisione.

Per capirci… 13 % 3 = 1

% e’ il segno che contraddistingue solitamente in informatica l’operazione di modulo.

L’operazione sopra avrebbe dato come risultato della divisione 4, e come resto 1. Concordate?

k, ora immaginate di fare quest’operazione tra numeri enormi, avremo risultati piccoli e gestibili, ma sareste in grado di predire tali risultati, senza eseguire l’intera operazione del modulo?

forse per l’operazione di modulo la cosa e’ semplicistica e forse anche il problema e’ semplificabile, ma nel caso dei bitcoin, viene applicata una funzione di hash piuttosto robusta (difficile ottenere lo stesso risultato con conti di complessita’ inferiore)

tutto il gioco si bassa sul costo di eseguire tali conti su di un calcolatore, e sul numero di persone che scambiano transazioni alla luce del sole…

la ricerca di un bitcoin, non e’ altro che la ricerca di una stringa di caratteri che abbia un determinato numero di 000000 nella parte iniziale di tale stringa/sequenza… piu’ sono gli zeri consecutivi, piu’ la difficolta’ della ricerca e’ alta (sistema inflazionistico intrinseco del sistema)

la funzione di hash prende quindi in ingresso il risultato della precedente computazione che aveva ottenuto un “bitcoin” (o hash con determinate caratteristiche: la sequenza di zeri), prende un numero che rappresenta la difficolta applicata (o numeri di zeri cercati), e un numero che rappresenta un il nostro tentativo di ricerca… ovvero, ogni volta che facciamo il calcolo, e non otteniamo quello che cerchiamo, avendo applicato la medesima catena di transazioni e difficolta’, dobbiamo cambiare qualcosa per ottenere forse un bitcoin, dobbiamo incrementare quindi questo terzo parametro, nella speranza di ottenere cio’ che cerchiamo

via via va a costruirsi una catena, e la catena piu’ lunga diventa il riferimento per tutti nella ricerca dei bitcoin successivi… per ottenere una catena lunga serve un enorme capacita’ calcolo e qui sta il punto di tutto, se gli onesti alla luce del sole sono piu’ di quelli che remano contro il sistema, il sistema e’ stabile, e sicuro

did I miss something? fate domande che cosi’ aggiungo info 🙂