Operating from secret hide-outs, activists of Poland's suspended Solidarity union movement are attempting to salvage the remnants of a once-mighty information network that challenged the Communist Party's traditional stranglehold on the mass media.

Just as freedom of information played a vital role in Solidarity's emergence, so too has a communications blackout been a key factor in the imposition of martial law. The new military authorities devoted enormous efforts to sealing off Poland from the outside world and preventing news from traveling within the country.

The importance of information in the battle between the government and Solidarity was illustrated by the decision to cut all telephone and telex lines several hours before the mass arrest of union activists Dec. 13. Deprived of communications, Solidarity officials remaining at liberty were prevented from organizing effective, coordinated resistance to the crackdown.

The government's next step was to order teams of workers to tear down Solidarity pamphlets from walls and billboards. Duplicating machines were confiscated; the sale of all kinds of paper was banned, and all but a handful of tightly controlled official newspapers closed.

Among the most rigorous of the martial-law decrees are those attempting to cut the flow of information. The penalty for producing unofficial leaflets is up to 10 years in prison.

Despite the Draconian restrictions, however, Solidarity has managed to maintain the skeleton of an information service. The first illegal handbill came out shortly after the declaration of martial law and was addressed to the inhabitants of Warsaw. Describing the crackdown as a brutal attempt at repression, it added, "We must not allow our Solidarity to be shattered--it is the greatest value at this moment."

Later that day, pamphlets were distributed in Gdansk, Warsaw, Krakow and other major cities calling for a general strike.

At first, with workers still occupying their factories in many parts of the country, it was possible for Solidarity activists to run off thousands of copies of special strike bulletins on factory printing presses. But this source dried up after the sit-ins were broken by riot police and troops.

Today Solidarity's information service is forced to operate in the deepest secrecy with a minimum of equipment and printing materials and an erratic distribution system. Those involved in producing and circulating the underground pamphlets know that, if caught, they could be sentenced to several years' imprisonment.

In view of these difficulties, the range and detail of underground Solidarity publications is remarkable. In Warsaw, they include a twice-daily information bulletin, a news sheet entitled News with its own logo, which appears roughly every second day, and a weekly called Voice of the People.

In addition, dozens of statements, appeals and petitions are in circulation. Frequently they are written in tiny script on scraps of paper folded so many times that they become scarcely legible. The aim is to escape detection during spot-checks by police on the streets or in trams and buses.

Before martial law, Solidarity bulletins were distributed throughout the country by a network of telexes, which connected union offices in factories and small towns. A type of chain letter system was employed in which every recipient was instructed to pass the information on to five more Solidarity offices. In Polish, this method of relaying information was described as a "Christmas tree" because it started from a single point and broadened at the base.

Solidarity officials estimated that, distributing information via the Christmas tree, they could get a message to every part of the country within two hours.

Today much the same system is being used--even if the technology is much more rudimentary than telex. All underground Solidarity bulletins bear the subheading: "Copy and pass on." If every reader makes six copies, the information spreads quickly.

A vital boost, of course, is given by foreign radio stations such as the Voice of America and Radio Free Europe. If their Polish-language services pick up information originating in Poland and beam it back to the country, circulation immediately becomes much wider.

Several days ago, a U.S. Embassy official was called into the Polish Foreign Ministry to receive a protest about the broadcasts. He was told that Solidarity statements circulated in only a couple of hundred copies within Poland itself--but, once picked up by VOA, they were heard by millions.

Fear of information getting back to Poland appears to have been the main reason for the official censorship on the dispatches of the hundred permanently accredited foreign correspondents in Warsaw. The Polish government announced Saturday that it was lifting censorship on foreign correspondents, but those reporters are still required to file their dispatches through the telex at the government's foreign press center. The censorship may have been backfiring by creating the impression of a country under siege.

At a press conference recently, the official Polish government spokesman read a string of unbelievable rumors that had appeared in the Western press ranging from reports of gangrene among detainees to hundreds of deaths in clashes between police and workers.

The correspondents countered by saying they could take no responsibility for the reports as regular communications with their news organizations had been cut and there was a deep mistrust of censored reports in the West.

The manipulation of the official news media has had a similar effect within Poland. After 15 months in which Polish journalists attempted to regain some credibility, there is now a mood of widespread disbelief in official information. Polish newspapers have reverted to the old form of dispatches employed before Solidarity's emergence in August 1980, with strikes described as "interruptions in the rhythm of production" and massive shortages of all consumer goods termed "temporary supply difficulties."

The result is a huge increase in audiences for foreign radio stations. Listening to Radio Free Europe has again become an obsession for many Poles despite the fact that audibility is poor because of heavy jamming. In some apartment buildings in Warsaw, dozens of families can be heard tuning in to the station.