Comment by adrian_b

Triple-key DES (DES-EDE) had already been proposed by IBM in 1979, in response to the criticism that the 56-bit keys of DES are far too short.

So practically immediately after DES was standardized, people realized that NSA had crippled it by limiting the key length to 56 bits, and they started to use workarounds.

Before introducing RC2 and RC4 in 1987, Ronald Rivest had used since 1984 another method of extending the key length of DES, named DESX, which was cheaper than DES-EDE as it used a single block cipher function invocation. However, like also RC4, DESX was kept as a RSA trade secret, until it was leaked, also like RC4, during the mid nineties.

IDEA (1992, after a preliminary version was published in 1991) was the first block cipher function that was more secure than DES and which was also publicly described.