1. An LDPC decoder comprising: a determined number of processing units operating in parallel, each processing unit being capable of successively receiving messages of a first type and of successively providing messages of a second type based on a first processing of the messages of the first type, and of receiving messages of the second type and of providing messages of the first type based on a second processing of the messages of the second type, the second processing being different from the first processing; storage means capable of containing first words and second words, each first word containing a juxtaposition of messages of the first type in a number equal to said determined number, and each second word containing a juxtaposition of messages of the second type in a number equal to said determined number; a message provision unit capable of: reading first words or second words from the storage means; providing to each processing unit, for each first read word, a message of the first type at a position in the first word which depends on the processing unit; and providing to each processing unit, for each second read word, a message of the second type at a position in the second word which depends on the processing unit; and a message write unit capable of: writing, into the storage means, first words, each first word containing messages of the first type, each provided by a different processing unit, each message of the first type being at a position in the first word which depends on the associated processing unit; and writing, into the storage means, second words, each second word containing messages of the second type, each provided by a different processing unit, each message of the second type being at a position in the second word which depends on the associated processing unit, wherein the message provision unit is further capable of providing said message of the first type at a position in the first word which depends on the first word and said message of the second type at a position in the second word which depends on the second word, or wherein the message write unit is further capable of writing each message of the first type at a position in the first word which depends on the first word and each message of the second type at a position in the second word which depends on the second word.